February 13th, 2019

GUN INFO 101 — Headspace Defined and Illustrated

Ultimate Reloader Brownells headspacing go gage gauge barrel gunsmithing
This illustration shows headspace measurement for the popular .308 Winchester cartridge, which headspaces on the shoulder. Image copyright 2015 Ultimate Reloader.

In this Brownells Tech Tip, Brownells gun tech Steve Ostrem explains what headspace is and why it’s one of the most critical measurements for nearly all firearms. Even if you’re an experienced rifle shooter, it’s worth watching this video to refresh your understanding of headspace measurements, and the correct use of “GO” and “NO-GO” gauges.

Headspace Definition
In firearms, headspace is the distance measured from the part of the chamber that stops forward motion of the cartridge (the datum reference) to the face of the bolt. Used as a verb, headspace refers to the interference created between this part of the chamber and the feature of the cartridge that achieves the correct positioning. Different cartridges have their datum lines in different positions in relation to the cartridge. For example, 5.56x45mm NATO ammunition headspaces off the shoulder of the cartridge, whereas .303 British headspaces off the forward rim of the cartridge.

If the headspace is too short, ammunition that is in specification may not chamber correctly. If headspace is too large, the ammunition may not fit as intended or designed and the cartridge case may rupture, possibly damaging the firearm and injuring the shooter. (Source: Wikipedia)

Forster Headspace diagram belted magnum rimfire

Go gauge gage NOGO no-go field gaugesHeadspace Gauges
Headspace is measured with a set of two headspace gauges: a “Go” gauge, and a “No-Go” gauge. Headspace gauges resemble the cartridges for the chambers they are designed to headspace, and are typically made of heat-treated tool steel. Both a “Go” and a “No-Go” gauge are required for a gunsmith to headspace a firearm properly. A third gauge, the “Field” gauge, is used (as the name implies) in the field to indicate the absolute maximum safe headspace. This gauge is used because, over time, the bolt and receiver will wear, the bolt and lugs compress, and the receiver may stretch, all causing the headspace to gradually increase from the “factory specs” measured by the “Go” and “No-Go” gauges. A bolt that closes on “No-Go” but not on “Field” is close to being unsafe to fire, and may malfunction on cartridges that are slightly out of spec. (Source: Wikipedia)

To learn more, read Brownell’s longer article Headspace Gauges and How to Use Them. Among other things, this explains the relative lengths of “Go”, “No-Go”, and “Field” gauges. The “Field” is actually the longest: “The GO gauge corresponds to the SAAMI (Sporting Arms & Ammunition Manufacturer’s Institute) minimum chamber length, while the FIELD gauge usually matches the maximum chamber depth, or slightly less. NO-GO gauges are an intermediate length between minimum and maximum, that, technically, is a voluntary dimension. A firearm that closes on a NO-GO gauge and does not close on a FIELD gauge may not give good accuracy and may have very short cartridge case life from the ammunition re-loader’s standpoint.”

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February 9th, 2019

Bet You Ain’t Seen This Before — Barrel-Indexing Rimfire Action

Bill Myers Indexing Action

The late Bill Myers was recognized as one of greatest rimfire gunsmiths who ever lived. Myers crafted many match-winning, record-setting rimfire benchrest rigs. Here we feature one of Bill’s most interesting creations — a clamping action that allows a rimfire barrel to be indexed (rotated) around the bore axis.

Bill was a creative thinker, and his own exhaustive testing has convinced him that barrel indexing can enhance accuracy in rimfire benchrest guns. Myers did acknowledge that, particularly with a very good barrel, the advantages of indexing may be subtle, and extensive testing may be required. Nonetheless, Myers believed that indexing could improve rimfire accuracy.

Indexing with the Myers’ Clamping Action
To index the barrel, Myers simply loosens the three clamping-bolts and rotates the barrel in the action. Because there is no thread to pull the barrel in or out, the headspace stays the same no matter how much the barrel is rotated. In other words you can rotate the barrel to any position on the clockface and the headspace remains unchanged.

Bill Myers Indexing Action
Bill Myers Indexing Action

The Challenge of Barrel Indexing
cone breech bill myers rimfire indexable actionWith a conventional barrel installation, employing a shoulder with a threaded tenon, it is difficult to index the barrel. Even with a cone breech (photo right) that eliminates the problem of extractor cuts, you’d have to use shims to alter the barrel index position, or otherwise re-set the shoulder each time you screwed the barrel in further.

Clamping Action Allows Barrel to Be Rotated to Any Position
Bill has come up with a masterful solution to barrel indexing. He designed and built his own prototype custom action that clamps the barrel rather than holding it with threads. The front section of the action is sliced lengthways, and then clamped down with three bolts. A special bushing (the gold-color piece in photos) fits between the barrel and the action. By using bushings of different inside diameters, Bill can fit any barrel up to an inch or so diameter, so long as it has a straight contour at the breech end. To mount the barrel, Bill simply places the fitted bushing over the barrel end-shank, then slips the “sleeved” barrel into the front end of the action. Tighten three bolts, and the barrel is secure.

Bill Myers Indexing Action

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February 5th, 2019

Blast from the Past — 6mmBR Drop-Port Viper

This week we return to our 6mmBR.com roots with an article on David Bergen’s slick 24″ Drop-Port Viper. This was one of the first 6BR rifles we featured. David, who hails from Belgium, developed this project over many months, and the gun proved to be a true tack-driver, with the ability to group in the Ones, even with the heavy boat-tail bullets. David talks about the build and his reloading methods while action designer Jerry Stiller provides technical insights into the design features of his Viper action.

Report by David Bergen

It was a long journey looking for the perfect custom action to build my new rifle. I searched the internet and visited various forums. I even re-read all my old Precision Shooting magazines to find what I was looking for. One evening I conferred by telephone with Mr. Jerry Stiller of Stiller’s Actions in Texas. He patiently answered all my questions. That moment I decided that I wanted a Viper Drop-Port action. [Editor: Sadly, the Viper Drop-Port is no longer in production.]

Component Selection
At the heart of this gun is a Viper action. This medium-sized action can handle cartridges from a small BR up to a 6.5-284. (Stiller’s smaller Cobra action is for PPC and BRs only.) The Viper is milled from aluminum. This keeps weight down while still allowing Vipers to have a large bedding surface like a Stolle Panda.

Viper Drop port action

At first I was a bit sceptical about the aluminum’s toughness, but Mr. Stiller informed me that the action is the perfect marriage between steel and aluminum. The bolt is hard-chromed and the action body is hard-anodized. This gives it two surfaces that resist wear and make an already-slick action even slicker. Stainless steel is used for all the heavy-stress points including barrel threads, locking lugs, and the rear camming surface. The bolt is made of steel with a very light, small-diameter firing pin to prevent primer piercing with heavy loads. Everything is held very concentric to the bore axis. The Viper is a very smooth action mainly because the design and the precise machining of the camming surfaces. Combined with optimal bolt-lift timing, this gives a smooth action. Stiller also keeps the tolerances very tight on these actions, though they are as fast-handling as any you can buy. The trigger is of course a Jewell BR model.

The rifle is chambered in 6mmBR Norma, my favorite cartridge. I have two HV-contour Shilen match barrels, both with 1 in 8″ twists and finished lengths of 24 inches. The chamber has a .266″ neck so neck-turning is necessary. Freebore is .060″ but combined with a 1.5° throat angle this lets me seat a wide range of bullets from 58 grains up to 107 grains.

The stock is a McMillan Edge with moulded-in gray and black marble swirl. I specified 60% black and dark and light gray both at 20%. I went with the Edge stock because I was always pleased with McMillan products and because it had a very low center of gravity. I wanted the barrels very low in the stock because I think it makes the gun track better.

Details of the Drop-Port–with VIDEO!
The visible part of the Drop-Port is a cartridge-sized cut-out in the floor of the action. This tapers into a funnel shape that lets the spent case fall nose-first through a single hole in the underside of the stock. The Drop-Port is carefully sized so that empty brass will fall through from gravity but a loaded round won’t. I’ve found that getting a BR case to eject 100% reliably in a standard action is not easy. The round is short and fat so it clears the chamber too early and the ejector pushes the cases out the extractor too fast. This can result in an empty case sitting in your action, no longer held by the extractor. Needless to say, this can slow you down during a stressful competition. When you get a Drop-Port you can forget all those problems.

Failure to eject is NOT going to happen with a Drop-Port. The system just works every time, and it’s FAST. Right-Click on the Media Player image and “Save As” to download a video (6.9 megs) showing me cycling the action during live fire.

One smart feature of the Drop-Port is the extractor location. A Remington extractor is located at the bottom of the bolt. This way the case is supported by the extractor until the front of the case lines up with the cut-out in the action. At that moment the front of the case tilts down and the rim slips out of the extractor. In the stock there is a funnel which collects the case. The case drops out of the rifle through a single small hole in front of the trigger guard.

Building an Accurate Load
Tools and Recipes

I start with new Lapua cases and after full-length sizing I trim them with a Wilson trimmer. Then I turn the necks for a .264″ neck diameter with a Lapua 105 seated in the brass. After fire-forming I use a “semi-custom” Harrell’s full-length sizing die with bushing. I use a .262 bushing with the moly-coated bullets. This Harrell’s die is the best I ever used — it gives very low run out. [Editor’s Note: Harrell’s stocks a number of dies with various internal dimensions. You send them three fire-formed cases and they’ll pick out a die that fits your brass the best. The cost is very reasonable.] Overall the excellent concentricity I’m seeing with my rounds is a combination of a superb chambering job, a neck-turned Lapua case and the Harrell’s sizing die. The die is supplied with a brass bushing that allows you to measure the amount of sizing you are doing.

For seating I use both a Wilson inline seater (hand die) and a Forster seating die that threads into a press. The latter gets the most use because I find it easier to use. Run out with both is around 0.001″ or better measured on the bullet.

Load development was very easy. I started with Varget and all loads … shot well. Vihtavuori N150 also shot very well with… moly-coated Lapua 105s. To my delight, the light bullets are also shooting very well in the 1:8″ twist. Nosler Ballistic Tips are giving very good results with a case full of N140. I’ve also tried N150, N540 and AA 2520. For all loads I’ve been using CCI BR4. Bullets are seated well into the lands with square marks showing. This gives an overall length around 59 mm (2.32″), depending on the bullet used.

Shooting the Rifle–How It Performs
The rifle is very easy to shoot and it is very accurate, but it had some drawbacks in the beginning. First there is the stock. It is designed for bench shooting and on a table it does this very well. I use a Caldwell front rest and a Protektor rear bag. When shooting prone I’ll also use the rest but the cheek weld is not ideal (the Edge was optimized for free recoil shooting from the bench). The rings that are supplied with the action are rather high. I looked around and found some that were lower. This made shooting easier, but I still wasn’t satisfied. The gun was a bit nose-heavy. There is a weight system built into the stock, but it wasn’t enough to bring the gun in balance. I like the balance point to be just in front of the receiver ring. So I cut the rear off the stock and put in a larger tube and turned some weights to put in it. I also made up an aluminum butt plate. Then I installed a Harrell’s brake to cut recoil to a minimum. With these modifications, the rifle is now shooting the way I want. I think the Edge stock is a very good design for benchrest shooting but for prone shooting it has some shortcomings. I think the MBR is a better stock for shooting prone.

Muzzle Brake–Less Recoil, Same Excellent Accuracy
After testing the barrel with different loads, I decided to put a brake on one barrel. Most of my guns are muzzle-braked and since I had two virtually identical barrels, I put a Harrell’s brake on one. The barrel had to be threaded to mount the brake and here I was a little concerned–I remembered the advice to “never mess with a winner”. The un-braked barrel was ultra-accurate and I was curious whether the process of fitting the brake might affect the accuracy.

Thankfully, my worries were unfounded. My targets showed no loss of accuracy — there was no evidence that the brake had caused any changes (except as to recoil). I have wondered though, perhaps the brake makes the gun more shootable and in that way compensates for some small accuracy loss that may be there? Whatever the case, the gun shoots just as tight as before, except now it’s a lot more user-friendly with less muzzle hop and less “push” on recoil.

This Rifle Literally Shoots Bug-Holes
And now I come to the end of the story. One day when testing the rifle at 100 meters (with brake installed), I spied a fly on the target. Well now, I thought, here is an interesting “precision shooting” challenge. I put the crosshair on the fly, squeezed the trigger, and the fly was history.

One shot, one kill. Now THAT is impressive precision. If you look closely you’ll see what’s left of Mr. Fly around the bullet hole. Or “bug-hole” as you Americans would say. This kind of performance is a real confidence-booster for the trigger-puller, let me tell you.

The Drop-Port — Simple Yet Advanced
Jerry Stiller tells us: “The drop-port ejects the case out the bottom of the action using only gravity. No ejector plunger is required so the system is as foolproof as anything can be. (A normal spring-loaded ejector creates an uneven load on one side of the case head.) Unlike other ejection systems, micro-ports etc., a Drop-Port doesn’t require tuning or adjusting, and just works. Many top shooters tell us they can cycle rounds faster with a Drop-Port action than with any other design.”

“The engineering of the Viper reflects some key design objectives. I wanted it to be able to fit standard commercially available stocks and have a barrel fit-up that was well known in the industry. I liked the idea of the larger bedding area and higher stiffness of the aluminum actions, so I chose the Panda footprint and barrel tenon for the Viper. I also made some changes to what was available at the time to make the product better. I used a smaller diameter firing pin to eliminate primer piercing, hard anodized all the aluminum parts for corrosion resistance and to make the surface hard and slick. The bolts are also coated for the same reasons.

Drop-Port technical drawing, Copyright © 2005, Stiller’s Precision Firearms, All Rights Reserved.

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February 3rd, 2019

Tuner Basics: Guide to Selection and Use of Barrel Tuners

Barrel Tuner Gene Bukys Shadetree Engineering

We’re starting to see barrel tuners employed in more competitive disciplines than ever — from 100 yards to 1000 yards. And even some varmint hunters are employing tuners or tuner/brakes now. This allows them to dial in accuracy with different loads (when shooting hundreds of rounds in a weekend). Here’s a quick over-view of the potential benefits of tuners.

Commentary by Mark Walker, Sierra Bullets Product Development Manager
This story originally appeared in the Sierra Bullets Blog. Visit SierraBullets.com.

Some people love tuners and others hate them. I use them on my rifles and I’ve had more than one person ask me why on earth I would put one of those things on my barrel. I’ve even had a national long range champion tell me to unscrew it and throw it into Lake Erie on my next trip to the pits at Camp Perry. However, there are other shooters that swear by them and have many match wins to back it up.

It’s an indisputable fact that tuners do have an effect on a rifle’s accuracy, however how much is somewhat open for debate. The large heavy target barrels that we use for benchrest or F-class may not be affected as much by a tuner as a lighter weight sporter type barrel. Each barrel that I’ve installed a tuner on not only showed improvement in accuracy but also displayed a wider load window. The increased accuracy is because of the ability to adjust the tuner to the load, however I believe the wider load window is due to the added weight of the tuner slowing down the barrel vibrations. These are both very important aspects of having a very accurate rifle.

Barrel Tuner Gene Bukys Shadetree Engineering

While better accuracy and a wider load window are two areas of improvement, I believe the most important feature of a tuner is the ability to adjust the tune during the middle of a match. This is especially important during matches where you must load all your ammo earlier and cannot make adjustments to the load during the match. If you happen to miss the load, instead of having to deal with a gun that isn’t shooting you can make an adjustment to the tuner and hopefully improve the accuracy of the rifle.

While I’ve laid out several ways that a tuner can help, there are also a few ways that tuners can cause problems. They add weight so if you are shooting a discipline that has weight limits on the rifle, you may not be able to install a tuner and still make weight. Sometimes, a barrel just doesn’t show improvement with a tuner installed. These are few and far between, but it is something to consider. If you make an adjustment to the tuner in a match, you need to make sure you move it in the right direction. Adjusting a tuner in the wrong direction can cause very large groups. And finally, if they aren’t tightened properly, tuners can come loose during firing which will cause a lot of problems as well.

As you can see, tuners have both positive and negative aspects. In my personal experience, the positives far outweigh the negatives so I will continue to use them on all of my competitive rifles. If you’ve been thinking about installing a tuner, hopefully some of the information that I’ve presented will help you make an informed decision.

Barrel Tuner

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January 29th, 2019

DIY Project — Install Jewell Trigger in F-Class Panda Action

Erik Cortina Lapua Jewell Trigger Panda Stolle Action Kelbly Kelbly's

In the video below, Forum member (and F-Class ace) Erik Cortina shows how to install a Jewell Benchrest trigger into a Kelbly F-Class Panda action. You could follow the same simple procedure to install a Jewell in a standard Panda action. Kelbly’s sell both standard and long versions of the F-Class Panda action. Both versions feature integral recoil lugs in the front.

To see more detail in this “how-to” video, you can zoom it to full-screen size. Simply click the full-screen icon (4-cornered frame) just to the right of the YouTube logo in the lower right.

Erik Cortina Lapua Jewell Trigger Panda Stolle Action Kelbly Kelbly's

Erik Cortina Lapua Jewell Trigger Panda Stolle Action Kelbly Kelbly's

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January 25th, 2019

The Dummy Round — Why You Need One for Chambering

Gre Tannel GreTan, Gre-Tan Rifles dummy round chambering gunsmith reamer chamber

How and Why to Create a Dummy Round
When you have a new custom rifle built, or a new barrel fitted to an existing rifle, it makes sense to create a dummy round. This should have your preferred brass and bullet types, with the bullet positioned at optimal seating depth. A proper dummy round helps the gunsmith set the freebore correctly for your cartridge, and also ensure the proper chamber dimensions.

Respected machinist, tool-maker, and gunsmith Greg Tannel of Gre-Tan Rifles explains: “I use the dummy round as a gauge to finish cut the neck diameter and throat length and diameter so you have [optimal] clearance on the loaded neck and the ogive of the bullet just touches the rifling.” He recommends setting bullet so the full diameter is just forward of the case’s neck-shoulder junction. “From there”, Greg says, “I can build you the chamber you want… with all the proper clearances”.

Greg Tannel has created a very helpful video showing how to create a dummy round. Greg explains how to measure and assemble the dummy and how it will be used during the barrel chambering process. Greg notes — the dummy round should have NO Primer and No powder. We strongly recommend that every rifle shooter watch this video. Even if you won’t need a new barrel any time soon, you can learn important things about freebore, leade, and chamber geometry.

This has been a very popular video, with 244,000 views. Here are actual YouTube comments:

That is the best explanation I’ve ever seen. Thank you sir. — P. Pablo

Nice video. You do a very good job of making this easy for new reloaders to understand. I sure wish things like this were available when I started reloading and having custom rifles built. Once again, great job, and your work speaks for itself. — Brandon K.

Beautiful job explaining chambering clearances. — D. Giorgi

Another Cool Tool — The Stub Gauge

When you have your gunsmith chamber your barrel, you can also have him create a Stub Gauge, i.e. a cast-off barrel section chambered like your actual barrel. The stub gauge lets you measure the original length to lands and freebore when your barrel was new. This gives you a baseline to accurately assess how far your throat erodes with use. Of course, as the throat wears, to get true length-to-lands dimension, you need take your measurement using your actual barrel. The barrel stub gauge helps you set the initial bullet seating depth. Seating depth is then adjusted accordingly, based on observed throat erosion, or your preferred seating depth.

Stub Gauge Gunsmithing chamber gage model barrel

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January 24th, 2019

How to Calculate Bullet RPM — Spin Rates and Stability

Spin rate stability bullet speed RPM Formula stabilization barrel twist
Photo by Werner Mehl, www.kurzzeit.com, all rights reserved.

Most serious shooters can tell you the muzzle velocity (MV) of their ammunition, based on measurements taken with a chronograph, or listed from a manufacturer’s data sheet. (Of course, actual speed tests conducted with YOUR gun will be more reliable.)

Bullet RPM = MV X 720/Twist Rate (in inches)

However, if you ask a typical reloader for the rotational rate of his bullet, in revolutions per minute (RPM), chances are he can’t give you an answer.

Knowing the true spin rate or RPM of your bullets is very important. First, spin rate, or RPM, will dramatically affect the performance of a bullet on a game animal. Ask any varminter and he’ll tell you that ultra-high RPM produces more dramatic hits with more “varmint hang time”. Second, RPM is important for bullet integrity. If you spin your bullets too fast, this heats up the jackets and also increases the centrifugal force acting on the jacket, pulling it outward. The combination of heat, friction, and centrifugal force can cause jacket failure and bullet “blow-ups” if you spin your bullets too fast.

Accuracy and RPM
Additionally, bullet RPM is very important for accuracy. Nearly all modern rifles use spin-stablized bullets. The barrel’s rifling imparts spin to the bullet as it passes through the bore. This rotation stabilizes the bullet in flight. Different bullets need different spin rates to perform optimally. Generally speaking, among bullets of the same caliber, longer bullets need more RPM to stabilize than do shorter bullets–often a lot more RPM.

It is generally believed that, for match bullets, best accuracy is achieved at the minimal spin rates that will fully stabilize the particular bullet at the distances where the bullet must perform. That’s why short-range 6PPC benchrest shooters use relatively slow twist rates, such as 1:14″, to stabilize their short, flatbase bullets. They could use “fast” twist rates such as 1:8″, but this delivers more bullet RPM than necessary. Match results have demonstrated conclusively that the slower twist rates produce better accuracy with these bullets.

On the other hand, Research by Bryan Litz of Applied Ballistics has shown that with long, boat-tailed bullets, best accuracy may be achieved with twist rates slightly “faster” than the minimum required for stabilization. The reasons for this are somewhat complex — but it’s something to consider when you buy your next barrel. If, for example, the bullet-maker recommends a 1:8.25″ twist, you might want to get a true 1:8″-twist barrel.

Calculating Bullet RPM from MV and Twist Rate
The lesson here is that you want to use the optimal RPM for each bullet type. So how do you calculate that? Bullet RPM is a function of two factors, barrel twist rate and velocity through the bore. With a given rifling twist rate, the quicker the bullet passes through the rifling, the faster it will be spinning when it leaves the muzzle. To a certain extent, then, if you speed up the bullet, you can use a slower twist rate, and still end up with enough RPM to stabilize the bullet. But you have to know how to calculate RPM so you can maintain sufficient revs.

Bullet RPM Formula
Here is a simple formula for calculating bullet RPM:

MV x (12/twist rate in inches) x 60 = Bullet RPM

Quick Version: MV X 720/Twist Rate = RPM

Example One: In a 1:12″ twist barrel the bullet will make one complete revolution for every 12″ (or 1 foot) it travels through the bore. This makes the RPM calculation very easy. With a velocity of 3000 feet per second (FPS), in a 1:12″ twist barrel, the bullet will spin 3000 revolutions per SECOND (because it is traveling exactly one foot, and thereby making one complete revolution, in 1/3000 of a second). To convert to RPM, simply multiply by 60 since there are 60 seconds in a minute. Thus, at 3000 FPS, a bullet will be spinning at 3000 x 60, or 180,000 RPM, when it leaves the barrel.

Example Two: What about a faster twist rate, say a 1:8″ twist? We know the bullet will be spinning faster than in Example One, but how much faster? Using the formula, this is simple to calculate. Assuming the same MV of 3000 FPS, the bullet makes 12/8 or 1.5 revolutions for each 12″ or one foot it travels in the bore. Accordingly, the RPM is 3000 x (12/8) x 60, or 270,000 RPM.

Implications for Gun Builders and Reloaders
Calculating the RPM based on twist rate and MV gives us some very important information. Number one, we can tailor the load to decrease velocity just enough to avoid jacket failure and bullet blow-up at excessive RPMs. Number two, knowing how to find bullet RPM helps us compare barrels of different twist rates. Once we find that a bullet is stable at a given RPM, that gives us a “target” to meet or exceed in other barrels with a different twist rate. Although there are other important factors to consider, if you speed up the bullet (i.e. increase MV), you MAY be able to run a slower twist-rate barrel, so long as you maintain the requisite RPM for stabilization and other factors contributing to Gyroscopic Stability are present. In fact, you may need somewhat MORE RPM as you increase velocity, because more speed puts more pressure, a destabilizing force, on the nose of the bullet. You need to compensate for that destabilizing force with somewhat more RPM. But, as a general rule, if you increase velocity you CAN decrease twist rate. What’s the benefit? The slower twist-rate barrel may, potentially, be more accurate. And barrel heat and friction may be reduced somewhat.

Just remember that as you reduce twist rate you need to increase velocity, and you may need somewhat MORE RPM than before. (As velocities climb, destabilizing forces increase somewhat, RPM being equal.) There is a formula by Don Miller that can help you calculate how much you can slow down the twist rate as you increase velocity.

CLICK HERE for Miller Formula in Excel Spreadsheet Format

That said, we note that bullet-makers provide a recommended twist rate for their bullets. This is the “safe bet” to achieve stabilization with that bullet, and it may also indicate the twist rate at which the bullet shoots best. Though the RPM number alone does not assure gyroscopic stability, an RPM-based calculation can be very useful. We’ve seen real world examples where a bullet that needs an 8-twist barrel at 2800 FPS MV, would stabilize in a 9-twist barrel at 3200 FPS MV. Consider these examples.

MV = 2800 FPS
8-Twist RPM = 2800 x (12/8) x 60 = 252,000 RPM

MV = 3200 FPS
9-Twist RPM = 3200 x (12/9) x 60 = 256,000 RPM

Of course max velocity will be limited by case capacity and pressure. You can’t switch to a slower twist-rate barrel and maintain RPM if you’ve already maxed out your MV. But the Miller Formula can help you select an optimal twist rate if you’re thinking of running the same bullet in a larger case with more potential velocity.

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January 24th, 2019

RetroMOD Project — Old eBay Rimfire Stock Reborn for F-Open

Anschutz 1411 stock gunsmithing project wood work palma rifle f-class F-Open stocking

Here is an interesting project by one of our Forum members. Martin C. (aka “Killick”) modified an Anschutz 1411 Match 54 rimfire prone stock to become a comfortable, great-tracking F-Class Open Division Stock. No Killick didn’t sacrifice a perfectly good rimfire rifle for this project — he bought the Anschutz stock by itself on eBay, then transformed it…

Killick explains: “This project started about seven years ago. I bought the Anschutz prone stock on eBay and whittled it a bit into a Palma rifle with a Barnard action and block and a Doan Trevor cheek piece and scope rail. Then about two years ago I decided to re-task the stock/action assembly into an F-Open rig. With more whittling, gluing, sanding, body fillering, sanding, filling, sanding, more sanding…and sanding, forming, priming, sanding, painting, waiting, painting, painting…painting and before you know it, Bob’s your uncle.”

Here is the eBay-sourced Anschutz 1411 stock, with new high-gloss blue finish, as initially modified for use in Killick’s centerfire Palma rifle. Looks nice!

Anschutz 1411 stock gunsmithing project wood work palma rifle f-class F-Open stocking

Next step was the addition of a 3″-wide wood fore-end for F-Open duties with front rest:

Anschutz 1411 stock gunsmithing project wood work palma rifle f-class F-Open stocking

Anschutz 1411 stock gunsmithing project wood work palma rifle f-class F-Open stocking

Almost done here… just needs priming and final painting:

Anschutz 1411 stock gunsmithing project wood work palma rifle f-class F-Open stocking

Here is Killick’s completed F-Open rifle with its much-modified Anschutz stock now finished in fire-engine red lacquer. This image shows the detail of the grip and customized cheekpiece.

Anschutz 1411 stock gunsmithing project wood work palma rifle f-class F-Open stocking

To learn more, visit Killick’s Anschutz Stock F-Class Project Thread on our Shooters’ Forum.

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January 21st, 2019

RifleShooter.com .308 Win Barrel Cut-Down Velocity Test

rifleshooter.com barrel .308 win cut-down test saw ammo GMM velocity magnetospeed

With barrels, one wonders “Can a little more length provide a meaningful velocity gain?” To answer that question, Rifleshooter.com performed an interesting test, cutting a .308 Win barrel from 28″ all the way down to 16.5″. The cuts were made in one-inch intervals with a rotary saw. At each cut length, velocity was measured with a Magnetospeed chronograph. To make the test even more interesting, four different types of .308 Win factory ammunition were chronographed at each barrel length.

rifleshooter.com barrel .308 win cut-down test saw ammo GMM velocity magnetospeed

READ RifleShooter.com .308 Win Barrel Cut-Down Test Article.

Test Barrel Lost 22.7 FPS Per Inch (.308 Win Chambering)
How much velocity do you think was lost, on average, for each 1″ reduction in barrel length? The answer may surprise you. With a barrel reduction from 28″ to 16.5″, the average speed loss of the four types of .308 ammo was 261 fps total. That works out to an average loss of 22.7 fps per inch. This chart shows velocity changes for all four ammo varieties:

rifleshooter.com barrel .308 win cut-down test saw ammo GMM velocity magnetospeed

Summary of Findings: The average velocity loss per inch, for all four ammo types combined, was 22.7 FPS. By ammo type, the average loss per inch was: 24.6 (Win 147 FMJ), 22.8 (IMI 150 FMJ), 20.9 (Fed GMM 168gr), and 22.5 (Win 180PP).

Interestingly, these numbers jive pretty well with estimates found in reloading manuals. The testers observed: “The Berger Reloading manual says for the 308 Winchester, ‘muzzle velocity will increase (or decrease) by approximately 20 fps per inch from a standard 24″ barrel’.”

How the Test Was Done
The testers described their procedure as follows: “Ballistic data was gathered using a Magnetospeed barrel mounted ballistic chronograph. At each barrel length, the rifle was fired from a front rest with rear bags, with five rounds of each type of ammunition. Average velocity and standard deviation were logged for each round. Since we would be gathering data on 52 different barrel length and ammunition combinations and would not be crowning the barrel after each cut, we decided to eliminate gathering data on group sizes. Once data was gathered for each cartridge at a given barrel length, the rifle was cleared and the bolt was removed. The barrel was cut off using a cold saw. The test protocol was repeated for the next length. Temperature was 47° F.”

rifleshooter.com barrel .308 win cut-down test saw ammo GMM velocity magnetospeed

CLICK HERE to Read the Rifleshooter.com Test. This includes detailed charts with inch-by-inch velocity numbers, multiple line charts, and complete data sets for each type of ammo. Rifleshooter.com also offers ballistics graphs showing trajectories with different barrel lengths. All in all, this was a very thorough test by the folks at RifleShooter.com.

Much Different Results with 6mmBR and a Longer Barrel
The results from Rifleshooter.com’s .308 barrel cut-down test are quite different than the results we recorded some years ago with a barrel chambered for the 6mmBR cartridge. When we cut our 6mmBR barrel down from 33″ to 28″, we only lost about 8 FPS per inch. Obviously this is a different cartridge type, but also our 6mmBR barrel end length was 5″ longer than Rifleshooter.com’s .308 Win start length. Velocity loss can be more extreme with shorter barrel lengths (and bigger cartridges). Powder burn rates can also make a difference.

Permalink Bullets, Brass, Ammo, Gear Review, Gunsmithing 4 Comments »
January 20th, 2019

The .20 Practical AR — Wicked Accuracy, Low Recoil

20 Practical AR uppers

The new .224 Valkyrie for AR15-platform rifles has garnered lots of attention lately. That new cartridge has gotten people thinking about the options for an AR shooter beyond the venerable .223 Remington (and 5.56x39mm NATO). While the .224 Valkyrie is good for shooting long heavy bullets (such as Sierra’s new 95gr SMK), there is a simpler, cheaper option for folks who favor “fast and light” — smaller, lower-mass bullets traveling at very high velocities. That option is the 20 Practical, which is simply a .223 Remington necked down to 20 caliber. This little cartridge can launch 40-grainers at over 3900 fps. That’s bookin’. This makes the 20 Practical a great choice for an AR-based varmint rifle.

20 Practical20 Practical Ultimate Varminter
A decade ago, as a “proof-of-concept”, AccurateShooter.com created a 20 Practical AR15 Ultimate Varminter with a custom 20-caliber upper from Robert Whitley of AR-X Enterprises, LLC. That project rifle was ultra-accurate — every 5-shot group out of the gun was less than the size of a dime. That gun was auctioned off, but Robert Whitley continues to produce custom 20 Practical AR15 uppers. (The 20 Practical cartridge is simply the .223 Rem necked down to 20 caliber — you can use standard .223 brass and load with standard.223 Rem dies. Just swap in a smaller expander and use smaller neck bushings.)

Robert reports that the accuracy of the first 20 Practical AR15 was no fluke. After building six (6) more 20 Practical uppers, he tested them for accuracy and they all shot great. These uppers feature DPMS low-pro receivers with side charging handles. They are fitted with PacNor 1:11″ twist, three-groove stainless barrels.

20 Practical AR uppers

Robert reports: “We have been making more 20 Practical AR15 uppers and I have to say I am astounded by the accuracy of these things. For shooting little tiny groups out of an AR15 with bullets going 3500+ fps, it’s hard to beat the 20 Practical. Today I test-fired six more uppers, all with 11-twist barrels. Three of the uppers had 24″ barrels, two had 20″ barrels, and one had an 18″ barrel (we call it ‘Stubby’).

20 Practical Reamer print

In four of these uppers I shot re-sized Winchester brass using 25.3 grains of WC844 powder with Berger 40gr BTHP bullets loaded at 2.225″ OAL (about .015″ off the lands). WC844 is inexpensive military surplus powder that is nearly identical to H335. I tried three different primers and the choice did not seem to matter (CCI BR4, Rem 7 1/2s and Win Small Rifle — the old silver ones). All these four uppers shot great. Here is an animated GIF with targets from uppers #6, 10, and 11. All groups are mag-fed, 5-shot groups shot at 100 yards using a front rest and rear bag.”

Targets Shot with Three Different 20 Practical AR Uppers

20 Practical AR uppers

For more information visit www.6mmAR.com, or contact Robert Whitley via email: rcw3 [at] erols.com.

Permalink Bullets, Brass, Ammo, Gear Review, Gunsmithing No Comments »
January 19th, 2019

Stub Gauges — Cool Tools That Perform Important Functions

Barrel Stub Gauge

Next time you have a barrel fitted, consider having your gunsmith create a “stub gauge” from a left-over piece of barrel steel (ideally taken from your new barrel blank). The outside diameter isn’t important — the key thing is that the stub gauge is created with the same reamer used to chamber your current barrel, and the stub must have the same bore diameter, with the same land/groove configuration, as the barrel on your rifle. When properly made, a stub gauge gives you an accurate three-dimensional model of the upper section of your chamber and throat. This comes in handy when you need to bump your case shoulders. Just slide a fired case (with spent primer removed) in the stub gauge and measure from base of case to the end of the gauge. Then, after bumping, re-measure to confirm how much you’ve moved the shoulder.

Barrel Stub Gauge

In addition, the stub gauge lets you measure the original length to lands and freebore when your barrel was new. This gives you a baseline to accurately assess how far your throat erodes with use. Of course, as the throat wears, to get true length-to-lands dimension, you need take your measurement using your actual barrel. The barrel stub gauge helps you set the initial bullet seating depth. Seating depth is then adjusted accordingly, based on observed throat erosion, or your preferred seating depth.

To learn more about stub gauges, read this AccurateShooter Forum Thread.

Forum member RussT explains: “My gunsmith [makes a stub gauge] for me on every barrel now. I order a barrel an inch longer and that gives him enough material when he cuts off the end to give me a nice case gauge. Though I don’t have him cut that nice-looking window in the side (as shown in photos). That’s a neat option. You can tell how much throat erosion you are getting from when it was new as well. For measuring initial seating depths, this is the most useful item on my loading bench next to calipers. Everyone should have a case gauge made by their smith if you have a new barrel put on.”

Forum member Lawrence H. has stub gauges made with his chamber reamers for each new barrel He has his smith cut a port in the stub steel so Lawrence can actually see how the bullet engages the rifling in a newly-cut chamber. With this “view port”, one can also see how the case-neck fits in the chamber. Lawrence tells us: “My stub gauges are made from my barrels and cut with my chamber reamers. With them I can measure where my bullets are ‘touching the lands’ and shoulder bump dimensions. This is a very simple tool that provides accurate information.” The photos in this article show the stub gauges made for Lawrence by his gunsmith.

Permalink Gear Review, Gunsmithing, Reloading 3 Comments »
January 11th, 2019

Bed It Right! Bedding Compounds Compared by Speedy

Marine-Tex Pillar Bedding Marine-Tex Bedding Block Aluminum Actions

A customer of well-known gunsmith (and Hall-of-Fame shooter) Thomas “Speedy” Gonzalez recently asked Speedy about bedding compounds. Speedy offered some interesting advice based on long-term testing of various materials. Speedy favors Marine-Tex because it is very stable over time, while other materials can shrink up to 6% dimensionally. A good bedding job should be a perfect fit to your barreled action. If the bedding material shrinks over time, that is NOT a good thing….

Speedy’s customer asked: “I know you’re not a Devcon man in regards to bedding compounds but I respect your input in such matters and my question is this in regard to aluminum actions. If Devcon was considered, for an aluminum action, would you prefer aluminum compound formula or steel formula? I personally prefer Devcon steel and Marine-Tex for steel receivers but my experience with aluminum is limited. Also do you have a release agent preference that works better with aluminum?”

Speedy answered: “My only preference of one epoxy over another is their stability over time. My buddy who works for the Texas State Weights and Measures Department had me cast several of the most common types of epoxies used for bedding into 1.000″ machined blocks. After one year of being kept in a controlled climate and measured for shrinkage monthly, the Marine Tex shrunk only 1/10th of 1% (i.e. 0.1%) whereas almost all the others (including Devcon Steel formula, Devcon Aluminum formula…) shrunk 3% to 6%. The only other compounds that matched the Marine Tex were Araldite 1253 and Araldite 2014, with the latter being quite expensive for daily use.”

Marine-Tex Pillar Bedding Marine-Tex Bedding Block Aluminum Actions

Speedy added: “The Marine Tex Grey has no atomized metal in its makeup even though it appears that it does. This can be proven by the use of a strong neodymium magnet. What is humorous to me is that people don’t like aluminum yet will bed their actions atop aluminum pillars that have twice the coefficient of expansion (COE) of steel. Like Devcon, it is what people have always done and used. Thus [they] perpetuate the same old stuff. That’s my two cents’ worth. But as I tell everyone, ‘I’ll tell you what I know or do, but it’s not my job to convince anyone to do it my way’.”

Release Agents — Try Shoe Polish
Regarding release agents, Speedy stated: “I use Kiwi Neutral or Tan shoe polish. This works great and you can find it anywhere. Do NOT use the black or brown as it will stick.”

Marine-Tex Pillar Bedding Marine-Tex Bedding Block Aluminum Actions

View More Photos of Speedy Inletting and Bedding Job
CLICK HERE to see an interesting bedding job done by Speedy using a custom titanium bedding block. Speedy notes, “The stock was a raw blank requiring full inletting for the action to fit properly plus the titanium block. All the loading ports, bolt handle cut, bolt stop, and trigger guard cuts were done with diamond tooling to eliminate fraying and/or delamination of the wood.” You’ll find more projects by Speedy on his Facebook Page. Speedy is in San Antonio, Texas now, and accepting new projects with his company S.G. Rifles LLC.

Permalink - Articles, Gunsmithing, Tech Tip No Comments »
January 8th, 2019

6.5×47 Tactical Tack-Driver — The Non-Creedmoor ‘Six-Five’

6.5x47 Lapua Tactical Rifle Ryan Pierce Brux Barrel H4350 Berger Hybrid

A couple seasons back we published our comprehensive 6.5×47 Lapua Cartridge Guide, researched by the 6.5 Guys. In case you’ve been wondering what kind of accuracy is possible for a tactical-type rifle chambered for this mid-sized cartridge, check out this tack-driver built by gunsmith Ryan Pierce. That’s a mighty impressive 0.206″ five-shot group fired with Berger 140gr Hybrids using a Brux cut-rifled barrel. The powder was Hodgdon H4350, a very good choice for this cartridge.

6.5x47 Lapua Tactical Rifle Ryan Pierce Brux Barrel H4350 Berger Hybrid

Ryan reports: “Here is a 6.5×47 I built for a customer. It features a trued Rem 700 action, Brux 1:8″ Rem varmint-contour barrel, Mcmillan thumbhole stock, Surgeon bottom metal, and 3-port muzzle brake. The customer’s preferred load is the same that has worked in the last couple dozen 6.5x47s I’ve built: 41.1-41.3 grains of H4350 with 140 hybrids .050″ off the lands. This should run about 2810-2815 fps from a 26″ barrel. The 3.128″ refers to length of a loaded round from the base to ogive including the Hornady ogive comparator tool.”

6.5x47 Lapua Tactical Rifle Ryan Pierce Brux Barrel H4350 Berger Hybrid

Yep, It Measures Up…
Lest anyone dispute Ryan’s measurement of this group (the internet is full of nay-sayers), 0.206″ is EXACTLY what we got when we measured this group using OnTarget software. See for yourself:

6.5x47 Lapua Tactical Rifle Ryan Pierce

Permalink Gear Review, Gunsmithing, Tactical 5 Comments »
January 1st, 2019

The Modern F-Open Rifle — Action, Stock, Optics, and Cartridge

.284 Win F-Class F-Open Rifle Emil Kovan Brux BAT M Master Class Bernosky

Emil Kovan is one of the top F-Class shooters in the world. He won the 2014 United States F-Open Championship, and finished second in F-Open Division at the 2016 Canadian National F-Class Championship in Ontario. He is a great shooter and a great gun-builder as well.

The Anatomy of a Modern F-Class Open Rifle

Report by Emil Kovan
Kovan Match Rifles LLC, www.matchrifles.com

“What are the best components for an F-Open class rifle, and why?” That’s a question that I get asked all the time and will try to answer in this article. Two months ago, I was contacted by Duane, a gentleman I met at the 2015 F-Class Nationals. He was interested in building a rifle with the new Master Class Low Profile F-Open Stock, created by Carl Bernosky and Alex Sitman of Master Class Stocks.

I have known Alex Sitman for many years, and use his stocks exclusively, but was not very familiar with his new Low Profile F-Open stock. After a brief conversation with Alex, I placed an order, and had the stock inletted and bedded at my shop in a month. My first impression was “Wow that’s a long stock” — the forearm is significantly longer than on the original Master Class F-Class prone stock. I bolted the barreled action in, and squeezed the end of the forearm and barrel together, the stock flexed a little bit, but not as much as other designs that I have tested. I think that’s due to having “more meat” in the receiver area. The full stock depth continues farther forward that on some other “low profile” designs. That makes the stock stiffer in the vertical plane, reducing the hinging effect forward of the action. The stock was finished in gloss black per the customer’s request. Interestingly, I found that the multiple layers of paint and clearcoat stiffened the stock up quite a bit.

CLICK IMAGE below for full-screen version
.284 Win F-Class F-Open Rifle Emil Kovan Brux BAT M Master Class Bernosky

Low Center of Gravity Tames Torque
Compared to the original Master Class F-Open stock, the barrel sits about an inch lower. Lower center of gravity equals less torque, and that is very important when shooting heavy bullets in fast twist barrels. Another significant improvement is that the toe of the stock is flat and parallel to the forearm. I added a 3/4″ track rail in the rear, and milled the underside of the fore-end to create two parallel “rails” in the front to help the stock track better.

One of the biggest reasons why I like Master Class stocks, is the pistol grip. I don’t shoot “free recoil” and a comfortable pistol grip is super important to me when selecting a stock. The new Master Class Low Profile stock shares the same grip as the old model. This allows the stock to accommodate either a “hard hold” style or a more free-recoil style of shooting — whatever the rifle’s owner prefers. This design versatility is one reason I recommend Master Class stocks. Shooters may experiment with either shooting style to find what suits them best.

.284 Win F-Class F-Open Rifle Emil Kovan Brux BAT M Master Class Bernosky

Cartridge Choice — A 40° .284 Win Improved
Duane decided to have the barrel chambered for my 284 KMR IMP (Improved) wildcat. What is .284 KMR IMP and why choose it over the straight .284 Winchester? Improved by definition means “made better”, I took a great cartridge, and modified it to increase capacity, reduce pressure, and increase brass life.

There are many “improved” variants of the original .284 Winchester: 7mm Walker, .284 Shehane, .284 Ackley and so on. My version, the 284 KMR IMP, shares the .010″ blown-out sidewalls of the .284 Shehane, but I have further increased the case capacity by changing the shoulder angle from 35 to 40 degrees. The 284 KMR IMP allows you to almost match magnum cartridge velocity in a standard-bolt-face action. If you want to run 180gr-class 7mm bullets over 2900 FPS, it is cheaper and more convenient to have a barrel chambered in 284 KMR IMP than to spend $650 for a magnum bolt.

Tuning Loads for the .284 Win Improved Cartridges
The 284 KMR IMP seems to have two nodes, one around 2820 fps and other at 2940 fps. My match load clocks at 2935 fps with single-digit ES. Note –I selected that load based on accuracy, NOT raw speed. A lot of novice (or hard-headed) shooters make the mistake to push their cartridges to the max, and disregard more accurate loads at lower velocity.

.284 Win F-Class F-Open Rifle Emil Kovan Brux BAT M Master Class Bernosky

The sport of F-Class is rapidly growing, and the equipment used is improving constantly. I remember that only few years ago, an F-Open rifle that could shoot sub-one-inch of vertical at 300 yards was considered competitive. Now, we are pursuing sub-one-inch vertical at 600 yards! It takes a great rifle to approach that goal, but it is also up to the shooter to learn and experiment as much as possible in order to achieve success.

Dies for an Improved .284 Win Cartridge
One of the biggest challenges in campaigning a wildcat cartridge has been obtaining great dies. When searching for custom dies, it almost seems like that the odds are stacked against us. The most common problem is wait-time — custom die orders can take months to be completed. Also, most custom die makers want you to send them two or three cases, each fire-formed three times. I find that funny because if could somehow properly size the cases for three fire-forming cycles, I would not need a sizing die.

.284 Win F-Class F-Open Rifle Emil Kovan Brux BAT M Master Class Bernosky

Custom-made dies should size the case just right, but sometimes the die’s internal dimensions are slightly off, and this leads to problem number two: dies sizing too much (or even worse) too little. I had a one “custom” die that would not size the bottom of the case enough. This made the extraction of fired cases very difficult. I feel that the best option (if available) for shooters interested in wildcat chambers is to have their gunsmiths make the dies. I offer that die-making service in addition to barrel chambering.

BAT Machine “M” Action
Duane decided to use a BAT M action for this rifle, and I think that he could not have made a better choice. We are blessed with many good match-quality receivers: Barnard, BAT, Borden, Kelbly, Nesika, and Stiller just to mention a few. These are all very well-made and suitable for F-Class. Among BAT Machine Co.actions, I like BAT models M, MB, and 3LL best. I prefer these because because of their size (large bedding footprint) smoothness, timing, options available, and last but not least visual appearance.

Trigger: I recommend and use Jewell triggers. Other good options are: Kelbly, CG Jackson (good 2-Stage) Anschutz (best 2-Stage for Bat and Kelbly actions), Bix’N Andy, and David Tubb.

Barrel: Duane made another good choice here. He decided to go with a Brux 1:8.5″-twist, 4-groove cut-rifled barrel. If you look at the F-Class and Long Range benchrest equipment lists, you will see that cut-rifled barrels are currently dominating. Many records have been shot with both button-rifled, and cut-rifled barrels. I have shot both, and prefer cut-rifled barrels. I am not saying that button-rifled barrels are not capable of shooting as well as cut-rifled barrels, but on average, in my experience, four out of five cut-rifled barrels (from top makers) will shoot well, vs. three out of five buttoned barrels. YMMV, but this is what I’ve observed.

Brux Barrels is not the only company that produces very accurate cut-rifled barrels. We know that Krieger, Bartlein, Satern, and Hawk Hill Custom all make fine cut-rifled barrels as well.

Scope: Duane’s rifle was fitted with a Nightforce 15-55x52mm Competition scope with DDR-2 reticle. This optic is ultra clear, reasonably lightweight (28 oz.), super reliable, and has 1/8 MOA clicks — what you want for long range F-Class competition. In this 15-55X NF model, I like the DDR-2 reticle best, because fine cross hairs (FCH) are hard to see in heavy mirage. The DDR-2 has a heavier horizontal line, with a center dot. March scopes are also very popular and very well-made.

.284 Win F-Class F-Open Rifle Emil Kovan Brux BAT M Master Class Bernosky

Thanks for reading, and keep ‘em in the middle…

Emil Kovan F-Class competition bio photoEmil Kovan Competition History:

– 2014 F-Class Open National Champion

– 2016 F-Class Open Canadian Championship, Silver Medal (tied for first on score)

– 2015 F-Class Open National Championship, Silver Medal

– F-Class Open National Championship Teams, 2015, 2014, 2013, Shooting Team Member

– Over 15 wins in Regional and State Championships in Palma, F-TR, F-Open

– 2013 U.S. National Team Member

– 2017 U.S. National Development Team Member

Permalink - Articles, Competition, Gunsmithing, Tech Tip 2 Comments »
December 31st, 2018

New Mag-Fed Action Optimized for 6 Dasher and 6BR Family

Borden super short 6 action 6mmBR Dasher BR Ackley BRA 6

The 6BR Improved cases have become very popular in tactical competitions. In fact the Precision Rifle Blog reports that the majority of Top 10 PRS and NRL shooters are now running some version of the 6mmBR Norma case — such as the 6mm Dasher, 6BRX, or 6BR Ackley. In fact “40% of those ranked in the top 10 in either league were running a 6mm Dasher”. This short, fat 6BR improved case can push the 100-107gr bullets to 2950+ fps, a well-known accuracy node. Yes the 6mm Creedmoor and 6XC can push heavy 6mm projectiles faster to be sure, but there is a trade-off in barrel life. The 6BR Improved cases represent a “sweet spot” for the tactical game, offering outstanding accuracy, with less recoil than bigger cartridges, including the 6.5 Creedmoor.

The only real downside to the short/fat 6BR-based cartridges is that they can be finicky when feeding from a magazine, at least without some modifications to the follower and feed lips. There are kits that can help with this, but now there is an even better solution — a premium custom action designed specifically to feed the 6mm Dasher (and similar cartridges) from a magazine. This action, the Borden Super Short 6, was recently, unveiled on Facebook by PRS competitor John Hargett. This action, available in both right- and left-hand versions, features a dedicated new Super Short 6 (SS6) magazine optimized for Dasher-sized cartridges. The bolt has a shorter throw than a standard Rem short action. We think this new action could become VERY popular with tactical shooters, and varmint hunters.

John Hargett says: “Installing spacer kits or possibly having a nose dive in full-size .308 mag is in the past! This will fit all 700 stocks and chassis and AICS bottom metal. So no need to change what you are already using. Borden creates a masterful action at an extremely affordable price.”

Borden super short 6 action 6mmBR Dasher BR Ackley BRA 6mm

Key Facts about the Borden Super Short 6 Action and SS6 Magazine:

1. Rem 700 Footprint
— The Borden Super Short 6 action is internally tailored to the 6mmBR cartridge and its wildcats, but externally maintains Rem 700 action dimensions. This means the action IS compatible with the stock and chassis you currently own. And, the Borden Super Short 6 comes in both right-hand and left-hand versions, with PVD coating available (on action and/or bolt).

2. Rem Trigger Compatibility — The Borden Super Short 6 action works with Rem-compatible triggers, and the actions are specifically timed to work with trigger of your choice.

3. Dasher-friendly New Mag Design — The patent-pending Super Short 6 magazine is sized right for the 6mm Dasher and all the 6BR family. The follower and feed lips are configured to allow smooth, reliable feeding with no “magazine nose dives”. Even with the optimal design, the SS 6 magazine will work with all chassis profiles and bottom metal made for AICS-type magazines.

Borden super short 6 action 6mmBR Dasher BR Ackley BRA 6mm

Here is the description from Borden Rifles website:

“The new action from Borden Accuracy (Borden Super Short 6) features a Rem 700 short action-compatible footprint with a shortened magazine well and shortened port set up specifically to reliably feed 6 BR, 6 Dasher, 6 BRA, 22 BR cartridges. The bolt has modified Borden bumps to aid in cycling in the dirty environment. The pictured action shows our standard bolt handle and tear drop knob. Production models will feature a handle that is threaded on the end so individuals can use their preferred knobs. I have been one of the individuals that developed the bolt timing and neutral handoff with the trigger for competition shooting to minimize rifle upset in the bags when closing the bolt. These actions will be available with either the neutral timed handoff or with about .03 to .035 inch cock on close. The cock on close option has much easier bolt lift that seems to be favored by PRS competitors. For now the bolts will have spiral flutes but future versions will have diamond flutes as an option. Development work will be done to also handle the .223 Rem and the PPC family.”

Precision Rifle Blog 6mmBR Dasher BR Ackley BRA 6mm

6mm Dasher and 6BR Wildcats Favored by Top PRS/NRL Shooters

According to the Precision Rifle Blog:

1. The vast majority of PRS Shooters surveyed are now shooting a 6mm cartridge of some kind.

2. While the 6mm Creedmoor is still very popular, the 6mm Dasher is now the #1 cartridge among leading PRS and NRL competitors surveyed. (SEE Chart HERE)

3. If you include the 6BRX, 6BRA, and original 6mmBR cartridge along with the 6mm Dasher, this full family of short, fat cartridges is now used by twice as many top PRS/NRL competitors as the 6mm Creedmoor. And the 6.5 Creedmoor has really fallen from favor.


Credit Boyd Allen for Borden Action product find. Credit PRB for data on PRS/NRL cartridge use.

Permalink Gear Review, Gunsmithing, New Product, Tactical 9 Comments »
December 29th, 2018

Got Vertical Fliers? Check Your Firing Pin and Ignition System

USAMU Handloading vertical dispersion ignition rimfire accuracy firing pin
Top to bottom – Remington firing pin assembly with ISS, Tubb SpeedLock alloy-composite system without ISS (current versions have dual, opposite-wound springs), and Remington short action firing pin assembly without ISS.

The U.S. Army Marksmanship Unit regularly publishes technical articles on the USAMU Facebook page. One informative USAMU article covered mechanical issues and related ignition irregularities that can cause vertical fliers even with good ammunition in an otherwise excellent rifle. We highly recommend you read this article, which offers some important tech tips.

USAMU handloading hump day

Vertical Dispersion: Mechanical/Ignition Issues?

Poor or inconsistent ignition has long been known to be one of the “usual suspects” when one encounters vertical fliers that just shouldn’t be there. By having a sense of some of the basic principles involved, and a few basic areas to check, the shooter may avoid colsiderable frustration, not to mention time, expensive loading components and barrel wear.

USAMU Handloading vertical dispersion ignition rimfire accuracy firing pinIs your well-built rifle of high-quality components plagued with vertical fliers across more than 1-3 handload combinations? Consider the bedding, crown and scope/sight mounts. Are they correct? If so, then you might check for ignition issues before boldly undertaking an extensive, expensive, and quite possibly fruitless quest for the “magic handload”.

SEEING IS BELIEVING: While the author had been aware for many years that poor ignition should be considered and ruled out when dealing with vertical fliers in an otherwise-excellent rifle, actually seeing the problem and its almost instantaneous cure really drove the lesson home.

He was working with a “dot” rifle – a .22 LR match rifle that really stacked bullets into little piles at 50 yards and beyond. With one lot of ELEY Tenex, it produced consistent “bughole” groups at 50, but with another, selected lot of Tenex, similar groups were regularly ruined by single, vertical fliers that did not appear in other rifles. Rather than spending days burning up expensive, select ammunition looking for “magic lots”, he contacted a well-respected rimfire gunsmith and explained the situation.

Without so much as batting an eye, the highly-experienced ‘smith tore into the rifle’s action, and quickly found the cause(s) of the problem. He discovered a demonstrably weak firing pin spring, plus a chip out of the face of the firing pin where it contacted the cartridge rim.

After replacing and tuning the offending parts, the rifle immediately began shooting tiny, bughole groups with the previously “unacceptable” lot of Tenex. Centerfire rifles can also benefit from ensuring positive, consistent ignition. A wise riflesmith is literally worth his weight in gold!

So, what are some issues we as shooters can inspect in our rifles to help determine if ignition woes could be part of our problem? At the club level, ask yourself if that “experienced” Remington, Winchester 70, or even Springfield-based match bolt gun you’re using is still running its’ original 40-80 year-old factory striker spring? If so, a new replacement is cheap insurance against current or future problems. (And BTW, it might be best to stick to the normal, factory-spec spring weight. A super-powerful spring can cause vertical, just as a weak one one can.) Along with that, a routine check for proper firing-pin protrusion is a quick preventive measure that can rule out potential issues.

Other areas to consider are the centering and consistency of the firing pin’s operation in the bolt. Admittedly, with the increasing use of precision-machined custom actions, this is becoming less an issue every day. Below is the firing pin assembly from a custom BAT action:

USAMU Handloading vertical dispersion ignition rimfire accuracy firing pin

However, particularly with factory actions, a very quick and easy check is to remove the bolt, let the firing pin go forward, and look at the firing pin tip through the firing pin hole. Is the tip off-center in the hole, and possibly striking it as it moves forward? Is the hole out-of-round or burred from being struck repeatedly? If so, a trip to the riflesmith is likely in order.

Similarly, machining issues in the bolt/firing pin system can lead to rough and erratic firing pin movement, in which the firing pin drags against an internal surface of the bolt. In high-quality rifles these issues are relatively rare, but not unheard-of, and it takes mere minutes to rule them out. It may be worthwhile to remove the cocking piece/firing pin/spring assembly and look for any unusual gouges, dings, peening, burrs or signs of abnormal wear.

This task is especially easy with Winchester 70s, Springfields, and the similar Mauser 98s, involving little more than the push of a button and unscrewing the cocking piece assembly. This is just one of the many reasons these tried-and-true actions have earned such a loyal following in the field, among hunters who must maintain their rifles away from a shop.

USAMU Handloading vertical dispersion ignition rimfire accuracy firing pin

Particularly with older rifles, watch for and remove excess grease (or even Cosmoline!) from both the firing pin assembly and inside the bolt. This can help improve firing pin speed and consistency. Other bolt-action designs may need a take-down tool or other measures.

As part of this inspection, AFTER ENSURING THE RIFLE IS UNLOADED, slowly cock the rifle, dry-fire, and repeat several times. Listen carefully near the action for inconsistency in the sounds it generates. Does the striker falling make the same sound each time? Do you hear or feel grinding upon operation? If so, where?

Be sure to check the operation of the cocking piece (bolt shroud), firing pin within the bolt shroud, the cocking piece cam and the rear of the bolt body where the cocking piece cam operates. As with our examination for abnormal wear marks discussed above, look for marks indicating roughness or a possible need for light polishing. Then, clean and lightly grease the bearing surfaces while you’re at it.

Remington 700 bolt shroud and cocking cam
Rem 700 bolt cocking cam

These are relatively easy checks that shooters can undertake to perform a preliminary inspection on their own. Other mechanical issues can also cause ignition issues, chiefly centered around the action of the trigger, sear and sear spring. If these are suspected, a trip to an experienced, qualified riflesmith for diagnosis is recommended. We hope you find this information helpful! Join us again next week, and in the meantime, enjoy the shooting sports safely!

Permalink Competition, Gunsmithing, Tech Tip No Comments »
December 29th, 2018

Laminated Wood Stocks — Gallery of Guns

March 1-8x24mm FFP scope
GRS Laminated Stock from Norway (Imported by EuroOptic Ltd.)

Some folks think of laminated stocks as modestly-priced, “low-tech” alternatives for varmint and hunting rifles. In fact, for shooting disciplines that do not demand ultra-light weight, good laminated stocks give up nothing in performance to the most sophisticated composite stocks. And with laminates, it is relatively easy to fine-tune fit and ergonomics to suit the individual shooter. Available in a wide choice of colors, laminated stocks can also be very handsome. In our Shooters’ Forum, you’ll find a thread showcasing laminated stocks. It’s worth viewing. There are many interesting designs, and a wide variety of rifles ranging from “walking varminters” to long-range prone rifles.

March 1-8x24mm FFP scope

FalconPilot’s Shehane Tracker in Sierra Laminate with Clearcoat

Shehane African Obeche Wood Laminated Hunter by Cigarcop
Shehane African Obeche laminated wood hunting rifle 250AI

20 Practical Varminter (UK Custom posted by PNSE)

Prone Rifle by Carl Bernosky (posted by 1Shot)

F-Class (Special) by Alex Sitman (posted by J. DeKort)

Veteran’s Team Rifle #2 by Doan Trevor

Permalink Gunsmithing, Hunting/Varminting 2 Comments »
December 27th, 2018

Save 15% Now on All McMillan Fiberglass Stocks

McMillan 15% Off stock fiberglass sale december 29 2018

Here’s a great deal if you need a high-quality tactical, F-Class, benchrest, high power, silhouette, ELR, or hunting stock. Right now McMillan Fiberglass Stocks is discounting ALL its stocks 15% (fifteen percent). That’s right, EVERY McMillan rifle stock in inventory is on sale NOW for fifteen percent (15%) Off. But you must act quickly! This special 15% Off Sale concludes at 11:59 pm MST on December 29, 2018. So you have two more days to shop. Remember, this sale applies to ALL McMillan stocks, but the sale ends at 11:59 PM on 12/29/2018. Use Code STOCK2019 during check-out to save 15%.


To Save 15% Use Promo Code STOCK2019 at Check-Out »

McMillan 15% Off stock fiberglass sale december 29 2018

Note — Along with the 15% Savings, Free Shipping applies to orders over $50, standard ground delivery in the Continental USA. Shipping charges on previous orders will not be reimbursed. This offer cannot be combined with other promotions or offers. Offer expires December 29th at 11:59 pm MST.

Permalink Gunsmithing, Hot Deals, Hunting/Varminting No Comments »
December 26th, 2018

The Cut-Rifling Process — A Short History and Demonstration

Pratt & Whitney Cut rifling hydraulic machine

You’ve probably heard of cut-rifling, but did you know this process was invented in Germany nearly 500 years ago? Read on to learn more about how a cut-rifled barrel is made…

The cut-rifling process, used by leading barrel-makers such as Bartlein, Border, Brux, Krieger, and Obermeyer, can yield a very high-quality barrel with a long useful life. Cut-rifled barrels have been at the top in short- and long-range benchrest competition in recent years, and cut-rifled barrels have long been popular with F-Class and High Power shooters.

You may be surprised to learn that cut-rifling is probably the oldest method of rifling a barrel. Invented in Nuremberg around 1520, the cut-rifling technique creates spiral grooves in the barrel by removing steel using some form of cutter. In its traditional form, cut rifling may be described as a single-point cutting system using a “hook” cutter. The cutter rests in the cutter box, a hardened steel cylinder made so it will just fit the reamed barrel blank and which also contains the cutter raising mechanism.

Above is a computer animation of an older style, sine-bar cut-rifling machine. Some machine features have been simplified for the purposes of illustration, but the basic operation is correctly shown. No, the cut-rifling machines at Krieger don’t use a hand-crank, but the mechanical process shown in this video is very similar to the way cut-rifling is done with more modern machines.

Kolbe Border Barrels Firearms ID

Read About Cut-Rifling Process at Border-Barrels.com
To learn more about the barrel-making process, and cut-rifling in particular, visit FirearmsID.com. There you’ll find a “must-read” article by Dr. Geoffrey Kolbe: The Making of a Rifled Barrel. This article describes in detail how barrels are crafted, using both cut-rifling and button-rifling methods. Kolbe (past owner of Border Barrels) covers all the important processes: steel selection, hole drilling, hole reaming, and rifling (by various means). You’ll find a very extensive discussion of how rifling machines work. Here’s a short sample:

“At the start of World War Two, Pratt & Whitney developed a new, ‘B’ series of hydraulically-powered rifling machines, which were in fact two machines on the same bed. They weighed in at three tons and required the concrete floors now generally seen in workshops by this time. About two thousand were built to satisfy the new demand for rifle barrels, but many were broken up after the war or sold to emerging third world countries building up their own arms industry.

Pratt & Whitney Cut rifling hydraulic machine

Very few of these hydraulic machines subsequently became available on the surplus market and now it is these machines which are sought after and used by barrel makers like John Krieger and ‘Boots’ Obermeyer. In fact, there are probably less of the ‘B’ series hydraulic riflers around today than of the older ‘Sine Bar’ universal riflers.

The techniques of cut rifling have not stood still since the end of the war though. Largely due to the efforts of Boots Obermeyer the design, manufacture and maintenance of the hook cutter and the cutter box have been refined and developed so that barrels of superb accuracy have come from his shop. Cut rifled barrel makers like John Krieger (Krieger Barrels), Mark Chanlyn (Rocky Mountain Rifle Works) and Cliff Labounty (Labounty Precision Reboring)… learned much of their art from Boots Obermeyer, as did I.” — Geoffrey Kolbe

Video find by Boyd Allen. Archive photos from Border-Barrels.com. In June 2013, Birmingham Gunmakers Ltd. acquired Border Barrels. Dr. Geoffrey Kolbe has set up a new company called BBT Ltd. which produces chamber reamers and other gunsmithing tools and gauges. (Thanks to L. Holland for the Kolbe update).
Permalink - Videos, Gear Review, Gunsmithing 5 Comments »
December 25th, 2018

The Art of Gun-Making — Remarkable Video from Beretta

Beretta shotgun technology robot video Human

Here’s a Christmas present to our readers from Beretta — an amazing video about gun-making. This movie, “Human Technology”, is a visual feast, and one of the best videos we’ve ever featured. It’s that good. You’ll see an amazing blend of ultra-modern manufacturing technology along with old-world artisanship — “a mesmerizing meld of the high-tech and the traditional”. (Daniel Xu, Outdoor Hub.)

“Human Technology is a singular and symbolic movie, its cast entirely made up of Beretta workmen, thus illustrating the perfect synthesis between craftsmanship and technology,” Beretta writes. This artistic movie by Ancarani Studio illustrates all the aspects of the manufacturing of a high-end Beretta shotgun. This video is a study in contrast. The movements of robotic assembly machines are juxtaposed with the centuries-old craftsmanship of stock carvers. Beautifully filmed and edited, this video should amaze and entertain anyone who loves fine firearms. (Full-screen HD Recommended.)

Beretta shotgun technology robot video Human

Beretta shotgun technology robot video Human

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