August 12th, 2017

Figure Out Exact Barrel Weight with PacNor Calculator

Online Pac-Nor Barrel Calculator

Can you guess what your next barrel will weigh? In many competition disciplines, “making weight” is a serious concern when putting together a new match rifle. A Light Varmint short-range Benchrest rifle cannot exceed 10.5 pounds including scope. An F-TR rifle is limited to 18 pounds, 2 oz. (8.25 kg) with bipod.

One of the heaviest items on most rifles is the barrel. If your barrel comes in much heavier than expected, it can boost the overall weight of the gun significantly. Then you may have to resort to cutting the barrel, or worse yet, re-barreling, to make weight for your class. In some cases, you can remove material from the stock to save weight, but if that’s not practical, the barrel will need to go on a diet. (As a last resort, you can try fitting a lighter scope.)

Is there a reliable way to predict, in advance, how much a finished barrel will weigh? The answer is “yes”. PAC-NOR Barreling of Brookings, Oregon has created a handy, web-based Barrel Weight Calculator. Just log on to Pac-Nor’s website and the calculator is free to use. Pac-Nor’s Barrel Weight Calculator is pretty sophisticated, with separate data fields for Shank Diameter, Barrel Length, Bore Diameter — even length and number of flutes. Punch in your numbers, and the Barrel Weight Calculator then automatically generates the weight for 16 different “standard” contours.

Calculator Handles Custom Contours
What about custom contours? Well the Pac-Nor Barrel Weight Calculator can handle those as well. The program allows input of eight different dimensional measurements taken along the barrel’s finished length, from breech to muzzle. You can use this “custom contour” feature when calculating the weight of another manufacturer’s barrel that doesn’t match any of Pac-Nor’s “standard” contours.

Caution: Same-Name Contours from Different Makers May Not be Exactly the Same
One final thing to remember when using the Barrel Weight Calculator is that not all “standard” contours are exactly the same, as produced by different barrel-makers. A Medium Palma contour from Pac-Nor may be slightly different dimensionally from a Krieger Medium Palma barrel. When using the Pac-Nor Barrel Weight Calculator to “spec out” the weight of a barrel from a different manufacturer, we recommend you get the exact dimensions from your barrel-maker. If these are different that Pac-Nor’s default dimensions, use the “custom contour” calculator fields to enter the true specs for your brand of barrel.

Smart Advice — Give Yourself Some Leeway
While Pac-Nor’s Barrel Weight Calculator is very precise (because barrel steel is quite uniform by volume), you will see some small variances in finished weight based on the final chambering process. The length of the threaded section (tenon) will vary from one action type to another. In addition, the size and shape of the chamber can make a difference in barrel weight, even with two barrels of the same nominal caliber. Even the type of crown can make a slight difference in overall weight. This means that the barrel your smith puts on your gun may end up slightly heavier or lighter than the Pac-Nor calculation. That’s not a fault of the program — it’s simply because the program isn’t set up to account for chamber volume or tenon length.

What does this mean? In practical terms — you should give yourself some “wiggle room” in your planned rifle build. Unless you’re able to shave weight from your stock, do NOT spec your gun at one or two ounces under max based on the Pac-Nor calculator output. That said, the Pac-Nor Barrel Weight Calculator is still a very helpful, important tool. When laying out the specs for a rifle in any weight-restricted class, you should always “run the numbers” through a weight calculator such as the one provided by Pac-Nor. This can avoid costly and frustrating problems down the road.

Credit Edlongrange for finding the Pac-Nor Calculator
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May 9th, 2017

High-Tech Honing — Major Advance in Barrel Making

Sunnen honing barrel hone CNC computer honer machine Pac-nor

Some custom barrel makers are now honing barrels (after drilling) to improve bore diameter uniformity, smooth the interior finish, and reduce barrel lapping times. For years, large-scale manufacturers of hammer-forged barrels have employed honing. Now the process is being used by smaller, “boutique” barrel-makers. This article explains how and why barrel honing is done. Take the time to watch the video. For anyone with an interest in barrel-making, this video is an eye-opener…

Barrel Honing Process Demonstrated (Worth Watching!):

Barrel Bore honing cut-rifled rifling hammer forging accurateshooter.com

For custom barrel makers, honing is a time-saver and cost cutter. A few minutes on a honing machine can cut lapping times in half, leaving a cross-hatched surface finish in single or low double-digit Ra. Honing is the same process used to make diesel fuel injectors with bore roundness and straightness controlled to fractions of a micron (<0.000040″), with surface finish Ra ≤0.15 µm (6 µin).

A key manufacturing process used for hammer-forged barrels is now getting attention from the makers of custom button-rifled barrels. This process is precision bore-honing. Honing produces a high-quality bore surface fast, which is critical to hammer forging. (Why is honing so important with hammer forging? Surface finish is the one feature of the barrel that cannot be controlled in hammer forging. Surface imperfections in a barrel blank tend to be amplified as the blank is formed on the rifling mandrel. And if the bore is chromed afterwards, imperfections in the surface finish become even more obvious.)

Honing dramatically improves bore diameter size uniformity and accuracy, surface finish and roundness throughout the length of the barrel. It can certainly be used in place of a pre-rifling lap. The chief difference between a lapped and honed bore is the direction of the finish lines in the bore. Honing leaves fine spiraling crosshatch lines, while a lap leaves lines going longitudinally in the bore. After rifling the manufacturer can remove the crosshatch finish with a quick lap if desired. Honing is fast, accurate, and can be automated. Its surface quality and geometry can duplicate lapping, except for the longitudinal lines of the lapped finish.

Frank Green of Bartlein Barrels told us: “We worked with Sunnen and we did all the initial testing on the prototype machine for them. The machine works great! We ordered and received last year a new manufactured machine with the changes we wanted on it and we just ordered a second one a month or so ago. Should be here next month.”

(more…)

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June 26th, 2016

Pre-Fit FIX — Savage Accuracy Improves with Criterion Barrel

Savage Criterion BarrelIn our Shooters’ Forum, you’ll find a lengthy thread about accuracy problems with a Savage LRPV, chambered in 6mmBR. The gun would repeatedly split groups at 100 yards, and at 300 yards, the “flyers” would open up the groups to 1.5 MOA or larger. Interestingly, the factory test target (at right) showed a split group — not a good sign.

The gun’s owner, forum member LR_Shooter, tried a variety of tweaks: “I did this, done that… [changed] torque, tang floated, bedded action, recut chamber, and [adjusted firing pin]”. But nothing really helped. Frustrated, LR_Shooter asked his fellow Forum members for help. Much advice was proffered, including the novel idea of removing the middle action screw in the Savage 3-screw target action. Some of the advice proved helpful, but none of the suggested remedies produced a major improvement. This rifle, out of the box, tossed flyers and no amount of tweaking (or changes in shooting technique) really cured the basic problem. That is, until, the factory barrel got replaced…

Savage Criterion Barrel

New Criterion Pre-Fit Barrel Works Wonders
LR_Shooter acquired a Criterion pre-fit barrel from Jim Briggs at Northland Shooters Supply (NSS). These pre-fits are designed for easy installation with the standard Savage barrel nut. Wouldn’t you know it, with a new 30″ heavy-contour barrel on the LRPV, the gun started shooting way better. No more crazy fliers, no more split groups, no more excessive vertical. And the improvement came without any other major modifications. LR_Shooter reports: “I got a replacement barrel from Jim at NSS. It is a 30″ bull Criterion barrel. So far, without playing with torque screws and having my old setup… I’m very satisfied with the barrel I got. Now I have no problem getting [groups] under 0.25 MOA. Finally this thing can shoot!” The targets below, shot with the new Criterion barrel, speak for themselves. The left target was shot at 100 yards, while the target on the right was shot at 300 yards (very impressive).

Targets Shot with Savage LRPV Fitted with Criterion Barrel
Savage Criterion Barrel

Read Thread on Savage Accuracy Issues Fixed By Criterion Barrel

Moral of the Story — Sometimes A New Barrel Really Is the Right Solution
All of us have struggled at times with a rifle that won’t live up to expectations. This Editor personally struggled for over a year with a .260 Rem Savage with a factory tube. The gun tended to split groups and the POI walked as the barrel heated. I tried one powder/primer combination after another, working through a variety of seating depths over many months. I was persistent. Out of stubbornness, I just believed that sooner or later I’d find the magic load.

Well folks, sometimes there’s really nothing you can do about a sub-par barrel. It is what it is. To really improve a gun’s accuracy (particularly a gun with a factory tube), you may need to open your wallet and get a quality aftermarket barrel. Spending months trying one recipe after another may simply be an overwhelming waste of powder, bullets, and your precious time.

Albert Einstein supposedly said: “Insanity is defined as doing the same thing over and over again, and expecting different results.” Well that sort of describes my efforts with my .260 Rem. Once I had enough evidence that my barrel split groups no matter what load combo (and seating depth) I tried, it was time to pony up for a new barrel. When I did finally screw on a nice PacNor 3-groove Supermatch, that Savage suddenly became a true tack-driver. As re-chambered in 6mmBR with the Pac-Nor, in calm conditions, my Savage will now consistently shoot in the twos with heavy bullets, and it can sometimes dip down into the ones with Berger 80gr flat-base bullets. The moral of the story here is simple — don’t waste weeks or months chasing your tail with a barrel that just won’t deliver (after a reasonable amount of testing). Save up for a custom barrel, get it chambered properly, and stop your cycle of frustration.

Contact Information for Northland Shooters Supply:
E-mail: briggs.j-b@q.com (that is Q.com not G.com)
Phone: (763) 682-4296
Fax: (763) 682-6098
Mailing address:
P.O. Box 333
Buffalo, MN 55313

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May 8th, 2016

Sunnen Barrel Honing System Used by Pac-Nor Barreling

Pac-Nor PacNor Barreling honing hone Sunnen lapping barrel
Pac-Nor Production Manager Casey Dichter says the Sunnen hone produces a consistency in bore diameter that is much superior to hand-lapping. The Sunnen machine has all but eliminated the standard pre-rifling lap. “You can really tell the difference between a bore that was honed before rifling and one that was [only] lapped”, notes Dichter.

Gun Barrel Honing System Hits Target for Pac-Nor Barreling
Manufacturing precision rifle barrels has always been something of an art that involves hand lapping of the bore surface twice, before and after the rifling profile is cut or swaged in by a rifling button. In fact, a bright, hand-lapped bore is considered one of the hallmarks of a precision rifle barrel, despite the inherent variations from manual work done by people who get bored and tired from the monotonous chore. Pac-Nor Barreling, Inc. set its sights on this issue more than a year ago and hit the X-ring with the newly developed Sunnen HTE honing machine. The machine has all but eliminated Pac-Nor’s pre-rifling lap, which is the more difficult and time-consuming of the two laps. Pac-Nor is also producing as many custom barrels as ever, but with a slightly smaller staff. “Our objectives with the hone were to build a better product with less labor, and the honing machine has exceeded my expectations,” said Pac-Nor Production Manager Casey Dichter. “The hone produces a consistency in bore diameter that is head and shoulders above lapping, within two to three millionths of an inch end-to-end when it’s really dialed in,” he said. “This, in turn, improves the consistency of the rifling process by minimizing variation in the depth of the grooves. We still finish lap after rifling, but it’s easier because we just polish off the fine crosshatch finish that may be left after honing and rifling.”

Pac-Nor PacNor Barreling honing hone Sunnen lapping barrel
The Sunnen hone secures the barrel blank in a 3-jaw chuck, with honing oil pumped into one end while the tool works from the opposite end. Sunnen’s specialized Long Bore Tool uses metal-bond diamond or CBN superabrasives to quickly remove reamer marks, waviness, tight spots and other imperfections left by upstream processes.

Honing is an ideal replacement for hand lapping barrel blanks before rifling. It quickly removes reamer scratches and surface waviness without labor-intensive hand lapping. A typical 600-grit abrasive can produce a 6-10 microinch Ra (0.15 to 0.25 µm) finish in a reamed barrel blank. By producing a consistent bore diameter (±0.0001″ or less), parallelism, roundness and surface finish end to end, honing yields more consistent performance from rifling buttons and cutters, resulting in a constant groove depth. The ideal bore geometry reduces distortion of the bullet shape.

Pac-Nor’s barrel-making process starts with cutting and facing premium bar stock, followed by gun drilling, done by four Pratt & Whitney twin-spindle machines and an Eldorado CNC twin spindle. After reaming, the barrels are gauged for size. Depending on the condition of the reamer, 0.0004″ to 0.0007″ of material is left in the bore. This must be manually lapped out or honed out to final size for rifling. “Everyone who works here has done hand-lapping,” said Dichter. “It’s an unpleasant job, particularly if the reamer is starting to get dull. Lapping may take 10 to 45 minutes, depending on the caliber of the barrel. We tried to shorten this, but when chatter marks get ‘ironed’ into the surface by the rifling button, the finish lap is even longer and more difficult, so there is no advantage. With lapping, too, there is potential for variation, simply because it’s a manual process. Lapping can also be a production limiter and in our region we have a very small labor force to draw on when we want to grow.”

Pac-Nor PacNor Barreling honing hone Sunnen lapping barrel
Pac-Nor cuts and faces premium bar stock, then gun drills on one of five twin-spindle machines, followed by reaming of the blanks. This rack of barrel blanks awaits completion.

The company had explored honing in the nineties, but re-visited the idea when Sunnen introduced its HTE honing machine in 2014. The HTE is a horizontal machine that can hone small-bore rifle barrels, with a diameter range of 0.150″ to 0.790” (4-20 mm), and lengths up to 60″ (1,524 mm). Designed specifically for long small bores, the machine features an extremely sensitive drive and tool feed system that provide maximum protection against tool overload/breakage. Tool specific force limits and run settings are stored in the touch-screen PC control, allowing the system to sense tight sections in the bore and correct them automatically.

Sunnen also developed a new Long-Bore Tool (LBT) designed to take on industry’s most difficult honing challenges in small bores of .17 caliber rifle barrels. The tool quickly remove reamer marks, waviness, tight spots and other imperfections left by upstream processes. The LBT utilizes metal-bond diamond or CBN super-abrasives for high productivity, long life and fast cycle times. Precision-machined of through-hardened tool steel, the LBT can produce bore accuracies of 0.000027″ (0.0006 mm) for diameter, roundness, and taper – from first part to last.

“We are currently honing about 80 percent of what we make and will do more as we acquire the tools in different calibers,” said Dichter. “Although there is a trade-off in cycle time and abrasive cost for additional honing, we are still able to run our reamers two to three times longer than when we lapped alone. With a hand lap, the time and effort increase when the reamer is getting dull.”

After honing, each barrel is inspected again before rifling with a pull-button. Pac-Nor makes its own Accu-Twist carbide rifling buttons and can provide different rifling styles, including polygonal, per the customer’s choice. A button is attached to a rod and the rod is pulled through the barrel. The company’s hydraulic rifling machine utilizes a CNC-machined twist bar with a helix angle that matches the twist rate requested by the customer. The final twist rate is confirmed afterward using a Barrel-Scan electro-optical twist measurement system.

The barrel is then stress-relieved in a tempering furnace, followed by contouring of the outer shape and final, finish lapping of the bore. “During the finish lap, you can really tell the difference between a bore that was honed before rifling and one that was lapped,” said Dichter. “You can easily sense any remaining tight or loose spots in the bore. The diameter uniformity and roundness of the honed bore are superb. The lap also feels different in a honed bore.”

Pac-Nor PacNor Barreling honing hone Sunnen lapping barrel

In competitive shooting where winning scores may be separated by thousandths of an inch, a few millionths of an inch improvement in the uniformity of a Pac-Nor barrel may make a big difference for a skilled shooter. For more information, visit www.sunnen.com or contact:

Sunnen Products Company
Mr. Bob Davis
Global Communications Mgr.
Sunnen Products Company
Tel: 314-781-2100
bdavis [at] sunnen.com

About Pac-Nor Barreling Inc.
Pac-Nor Barreling is a true custom manufacturer catering to bolt-action rifle shooters. The company’s principle markets are law enforcement, military, competitive shooters and hunters. Started in 1984 by avid shooter and company President Chris Dichter, Pac-Nor is now in its second generation under his son, Casey. In addition to barrel manufacturing, the shop will install the barrel on a customer’s action, or add features such as muzzle brakes or fluting on bolts and barrels etc.

The shop runs two shifts per day. A day shift of ten people produces 30-40 custom barrels of different calibers in 416R stainless or chrome-moly steel. A night shift of three people produces one type of barrel — about 50 AR-15 barrels per day for a rifle OEM.

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October 17th, 2015

Online Barrel Weight Calculator from Pac-Nor

Online Pac-Nor Barrel Calculator

Can you guess what your next barrel will weigh? In many competition disciplines, “making weight” is a serious concern when putting together a new match rifle. A Light Varmint short-range Benchrest rifle cannot exceed 10.5 pounds including scope. An F-TR rifle is limited to 18 pounds, 2 oz. (8.25 kg) with bipod.

One of the heaviest items on most rifles is the barrel. If your barrel comes in much heavier than expected, it can boost the overall weight of the gun significantly. Then you may have to resort to cutting the barrel, or worse yet, re-barreling, to make weight for your class. In some cases, you can remove material from the stock to save weight, but if that’s not practical, the barrel will need to go on a diet. (As a last resort, you can try fitting a lighter scope.)

Is there a reliable way to predict, in advance, how much a finished barrel will weigh? The answer is “yes”. PAC-NOR Barreling of Brookings, Oregon has created a handy, web-based Barrel Weight Calculator. Just log on to Pac-Nor’s website and the calculator is free to use. Pac-Nor’s Barrel Weight Calculator is pretty sophisticated, with separate data fields for Shank Diameter, Barrel Length, Bore Diameter — even length and number of flutes. Punch in your numbers, and the Barrel Weight Calculator then automatically generates the weight for 16 different “standard” contours.

Calculator Handles Custom Contours
What about custom contours? Well the Pac-Nor Barrel Weight Calculator can handle those as well. The program allows input of eight different dimensional measurements taken along the barrel’s finished length, from breech to muzzle. You can use this “custom contour” feature when calculating the weight of another manufacturer’s barrel that doesn’t match any of Pac-Nor’s “standard” contours.

(more…)

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September 20th, 2014

Life Lesson: Every Barrel is Unique. Same Load Registers 4 Different Velocities in 4 Different Barrels

Put the same load in a variety of barrels (with the same length and chamberings) and you’ll see a wide variance in muzzle velocity. In fact, it’s not unusual to see up to 100 fps difference from one barrel to the next. We demonstrated this with a comparison test of Lapua factory ammo.

Chron Testing Lapua Factory Ammo
At our Southern California test range, we chronographed Lapua 105gr 6mmBR factory ammo in three different 8-twist barrels of similar length. The results were fascinating. Lapua specs this ammo at 2790 fps, based on Lapua’s testing with its own 26″ test barrel. We observed a speed variance of 67 fps based on tests with three aftermarket barrels.

barrel speed testing

Brand ‘S’ and Brand ‘PN’ were pre-fit barrels shot on Savage actions. Brand ‘K’ was fitted to a custom action. All test barrels were throated for the 100-108 grain bullets, though there may have been some slight variances in barrel freebore. With a COAL of 2.330″, the rounds were “jumping” to the rifling in all barrels. Among the four barrels, Brand ‘PN’ was the fastest at 2824 fps average — 67 fps faster than the slowest barrel. Roughly 10 fps can be attributed to the slightly longer length (27″ vs. 26″), but otherwise this particular barrel was simply faster than the rest. (Click Here for results of 6mmBR Barrel Length Velocity Test).

Results Are Barrel-Specific, Not Brand-Specific
These tests demonstrate that the exact same load can perform very differently in different barrels. We aren’t publishing the barrel-makers’ names, because it would be wrong to assume that ‘Brand X’ is always going to be faster than ‘Brand Y’ based on test results from a single barrel. In fact, velocities can vary up to 100 fps with two identical-spec barrels from the SAME manufacturer. That’s right, you can have two 8-twist, 26″ barrels, with the same land-groove configuration and contour, from the same manufacturer, and one can be much faster than another.

Don’t Demand More Than Your Barrel Can Deliver
We often hear guys lament, “I don’t get it… how can you guys get 2900 fps with your 6BRs and I can only get 2840?” The answer may simply be that the barrel is slower than average. If you have a slow barrel, you can try using more powder, but there is a good chance it may never run as fast as an inherently fast barrel. You shouldn’t knock yourself out (and over-stress your brass) trying to duplicate the velocities someone else may be getting. You need to work within the limits of your barrel.

Factory Ammo Provides a Benchmark
If you have a .223 Rem, 6BR, .243 Win, 6.5×47 Lapua, 6.5×55, .308 Win, 30-06, or 300 WM Rifle, we recommend you buy a box of Lapua factory-loaded ammo. This stuff will shoot great (typically around half-MOA), and it can give you a baseline to determine how your barrel stacks up speedwise. When you complete a new 6BR rifle, it’s wise to get a box of the factory ammo and chronograph it. That will immediately give you a good idea whether you have a slow, average, or fast barrel. Then you can set your velocity goals accordingly. For example, if the factory 6BR ammo runs about 2780-2790 fps in your gun, it has an average barrel. If it runs 2820+ in a 26″ barrel (or 2835 fps in a 28″), you’ve got a fast tube.

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