January 24th, 2019

SHOT Show 2019 — Eye-Catching Products

Shot show 2019 eley

There are tens of thousands of products on display at SHOT Show, the world’s largest firearms industry trade show. We visited dozens of manufacturers to see their featured items on display. Here are our selections of interesting products as well as some eye-catching product displays. Check out the cutaway Redding dies, the Norma giant plexiglass bullet shell.

Volquartsen .22 LR Ultralite with ModShot Carbon Stock, 3.8 LBS

Volquartsen ultralite ModShot carbon .22 LR rimfire rifle

Volquartsen showcased a radical rimfire rifle with “carbon everything”. Designed for rapid-fire Steel Challenge games, this unique rig has a carbon-wrapped barrel, carbon buttstock shaft with an aluminum buttplate, and a carbon fiber handhold forward of the action. The ModShot stock secures the bottom of the action, provides attachment points for rear section and front handhold. Total weight (without optics) is just 3 pounds, 13 ounces! MSRP is $1733.00. Our hunting editor, Colton Reid, said this “bare bones” carbon-enhanced design could be adapted for an ultralight centerfire hunting rifle under 5 pounds.

Redding Cutaway FL and Neck Sizing Dies

Redding Cutaway Sizing and Seating FL bushing full lenght micrometer Dies

At the Redding booth, we saw interesting sets of “cutaway” sizing dies. It was cool to see the insides of various types of dies. In the photo above the top two dies are micrometer-top dies. Below are three sizing dies: neck-sizing bushing die at left, a “plain” full-length sizing die in the middle, and a bushing full-length sizing die on the right. The bushing FL die would be our first pick — it allows you to size the entire body of the case, while adjusting neck tension (and bullet “grip”) with the neck bushings.

F-Open Champion with Kestros ZR Stock

Kestros ZR McMillan

Today, January 24th, Norm Harrold, the current F-Open 2018 national champion and 1000 yard record holder, appears at the McMillan booth. In the video above he’s holding the advanced, long-wheelbase Kestros ZR stock he used to set the new National Record and capture his F-Open title. Norm will explain the features of this stock that make it shoot so well. The Kestros ZR’s low COG and long wheelbase help the stock track and resist torque.

Christensen Arms Modern Precision Rifle

SK Ammunition .22 LR rimfire sheet cartridge

Our buddy Jason Baney was mighty impressed with the Modern Precision Rifle from Christensen Arms. With a handsome desert bronze finish, this rifle features carbon-wrapped lightweight barrel, carbon handguard/forearm, and carbon cheek piece. The folding buttstock folds quickly and secures with a magnetic lock. The rifle comes with a sub-MOA accuracy guarantee, and is available in 8 chamberings: .223 Rem, 6.5 Creedmoor, 6.5 PRC, .308 Win, 300 PRC, .300 Win Mag, .300 Norma Mag, and .338 Lapua Mag. Jason was so impressed with this $2295 rifle he said: “this could be my next hunting field rifle”. He said the folding stock really is an advantage when trekking long distances.

Rimfire Cases — How They Are Formed

SK Ammunition .22 LR rimfire sheet cartridge

At the Capstone Precision Group booth, we saw a long sheet of shiny brass metal. We were fascinated. This sheet illustrated how SK .22 LR casings are created from brass, started with a dime-sized flat circle, then ending with an extend narrow cylinder. This then becomes the case which receives the priming material (in the rim), powder and bullet. This is not identical to the actual factory production process, but it does show the key stages of rimfire case “punching” and drawing.

Frankford Arsenal New Compact Rotary Tumbler

SK Ammunition .22 LR rimfire sheet cartridge

Rotary tumblers do a fine job cleaning brass with media in liquid solution. There are many large rotary tumblers on the market. But frankly most are bigger than needed by rifle shooters who might just clean 100-200 pieces of brass at a time. Frankford Arsenal developed a smaller tumbler that runs smaller batches efficiently. Good idea. Look for this product at MidwayUSA in a few months. It should be significantly cheaper than Frankford Arsenal’s large, 7-liter Platinum tumbler which sells for $165.00 on Amazon.

Norma’s Giant See-Through Cartridge Display

Norma bullets brass Ammunition giant cartridge model display

Norma, maker of excellent brass, bullets, and loaded ammunition, had a eye-catching prop for displaying Norma bullets and cartridge brass. Over four feet long, this one-of-a-king plexiglass cartridge half-model held hundreds of projectiles and casings. Eye-catching for sure.

AMP Mark II — Runs Longer, Cooler, And Does .50 BMG

SK Ammunition .22 LR rimfire sheet cartridge

The makers of the Annealing Made Perfect (AMP) electro-induction annealing machine showcased a new, upgraded Mark II model. The new Mark II machine looks similar on the outside, but has a number of enhancements. It has bigger strong fans so it ran process more cases before you need to take a break to let the machine cool down. In addition, the Mark II now has a “super-sized” case chamber that can hold virtually any size case — all the way up to the .50 BMG. We watched as the AMP 2 annealed a jumbo .50 BMG in just a few seconds. Very impressive. For more info and pricing, visit www.AMPannealing.com.

Parting Shot — Goblin Green Race Pistol

eley green pistol 1911 race gun

Eley, the UK-based rimfire ammo maker, had a couple wild-looking race guns on display. This Metallic green stunner features a massive compensator, relieved slide (for faster cycling), and a color-coordinated C-MORE Reflex sight on top. Inconspicuous, this pistol is not!

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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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