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 from Sunnen Products Co. is an eye-opener.
Barrel Honing Process Demonstrated (Worth Watching!):
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.
In 2015 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 … a new manufactured machine with the changes we wanted on it and [subsequently] ordered a second one.”
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.
Sunnen states that: “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. 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.”
Computer-Controlled Bore-Honing
Honing can be done with great precision through the use of advanced, computer-controlled honing machines. Sunnen Products Company offers an advanced machine for .17 to .50-caliber barrels (see control panel below). The spindles on this machine can correct bore size imperfections so small only an air gauge can measure them. The consistency this allows improves bore uniformity, which, in turn, produces more accurate barrels for the precision market.
Sunnen Products Company is the world’s largest vertically-integrated manufacturer of honing systems, tooling, abrasives, coolants, and gauging for precision bore-sizing and finishing. Sunnen’s customers include manufacturers of diesel and gas engines, aerospace components, hydraulic components, oil field equipment, and gun/cannon barrels. Sunnen employs more than 600 people worldwide.
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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 some years ago, 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 Velocity Variance
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).
IMPORTANT: 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, 6mmBR, .243 Win, 6.5×47 Lapua, 6.5 Creedmoor, 6.5×55, .308 Win, .30-06 Springfield, or .338 LM 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. [Editor’s NOTE: The original test was conducted in 2008. The velocity of current-production Lapua factory ammo might be higher or lower, so your results may vary.]
When you complete a new 6mmBR rifle, it’s definitely smart 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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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 some years ago, 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 Velocity Variance
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).
IMPORTANT: 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, 6mmBR, .243 Win, 6.5×47 Lapua, 6.5 Creedmoor, 6.5×55, .308 Win, 30-06, or .338 LM 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. [Editor’s NOTE: The original test was conducted in 2008. The velocity of current-production Lapua factory ammo might be higher or lower, so your results may vary.]
When you complete a new 6mmBR rifle, it’s definitely smart 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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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 from Sunnen Products Co. is an eye-opener.
Barrel Honing Process Demonstrated (Worth Watching!):
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.
In 2015 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 … a new manufactured machine with the changes we wanted on it and [subsequently] ordered a second one.”
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.
Sunnen states that: “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. 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.”
Computer-Controlled Bore-Honing
Honing can be done with great precision through the use of advanced, computer-controlled honing machines. Sunnen Products Company offers an advanced machine for .17 to .50-caliber barrels (see control panel below). The spindles on this machine can correct bore size imperfections so small only an air gauge can measure them. The consistency this allows improves bore uniformity, which, in turn, produces more accurate barrels for the precision market.
Sunnen Products Company is the world’s largest vertically-integrated manufacturer of honing systems, tooling, abrasives, coolants, and gauging for precision bore-sizing and finishing. Sunnen’s customers include manufacturers of diesel and gas engines, aerospace components, hydraulic components, oil field equipment, and gun/cannon barrels. Sunnen employs more than 600 people worldwide.
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What’s a “Frankengun”? Well it’s a one-of-a-kind rifle that has been pieced together from a variety of different parts and components. It might be a little bit Bolt Gun mixed with a little bit AR-15. Or it might feature some home-made components unlike anything you’ve seen before.
We’ve selected these four Frankengun rifles from a current thread in our Shooters’ Forum.
Frankengun #1 — The EXO (as in Exo-Skeleton)
Forum member jm850 calls this tube-framed wonder the EXO (as in “exo-skeleton”). He says: “This is a prototype I designed around a few core concepts that stick out to me on a traditional configuration. Eliminating stresses, lowering recoil moment, and improved barrel cooling. I’m really happy with it so far.”
The EXO is a very unique rifle. We’ve never seen anything like this since the late Shelley Davidson’s famous Tinkertoy Rifle, a brilliantly innovative 30BR that actually won matches. The Tinkertoy, shown below, was truely radical, but it worked ! Could this have been an inspiration for jrm850’s EXO rifle?
Frankengun #2 — Moosberg MVG in LSS Stock with BipodeXt
Forum member BallisticXLR has created something very weird to say the least. It started out as a basic, bone-stock Mossberg MVP Varmint in .223 Rem. Then the transformation began: “I replaced everything except the receiver. It now has an LSS stock, PSG-1 grip from DPMS, XLR butt stock, PT&G lug and barrel nut, Columbia River Arms 26″ barrel with Sonoran coral snake Cerakote, A2 flash hider, Timney and Jard triggers (depending on what I’m doing), and a USO B17 which is now a USO 3.8-22×44.” That long extension tube under the chassis is a BipodeXt from Accuracy Solutions.
Frankengun #3 — A Chassis Rig in 25 Creedmoor
This Frankengun belongs to Forum member Geraldgee. This “black and blue” rig features a mag-fed Kelbly Atlas action in a McCree’s Precision G10 Chassis. The barrel is a Bartlein Rem Varmint Contour, 1:7.5″-twist 4 Groove, chambered for the 25 Creedmoor. There are some interesting .25-Cal bullets coming on the market now. You can make the brass by expanding 6mm Creedmoor, or necking down 6.5 Creedmoor.
Frankengun #4 — MDT Chassis, Fore-end Whittled by Spook
Here’s a real collection of odds and ends, but Forum member Spook says it shoots well, and is a great example of “Left-over parts made useful again”. This mix-n-match Frankengun features a Remington M7 action with PT&G bolt. The barrel is a stainless Pac-Nor chambered in 6mm SLR. The barreled action is carried in an MDT Chassis with rear folding buttstock. Up front is something unusual, a Delrin fore-end that owner Spook “whittled in the mill”.
Frankengun #5 — 6.5×47 in Accuracy Int’l Stock
CLICK photo for full-screen version.
Forum member CT10Ring kicked off the Frankengun thread with this rifle. It’s actually not that shocking, but you rarely see a BAT action in an Accuracy International stock. The BAT VR action is mated to an AI Mag and set up in an AI folding stock. On top is an “old school” Nightforce Benchrest scope. The barrel is a very heavy Krieger chambered for the 6.5×47 Lapua. CT10Ring say the barrel alone weighs about 9 pounds, and the gun “shoots better than [he] can”.
Post Pictures of Your Frankenguns in our Forum
So do you have a favorite Frankengun resting in your gun safe? If you do, visit our Shooters’ Forum and post a description and some photos in the Frankengun thread.
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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 some years ago, 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 Velocity Variance
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).
IMPORTANT: 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, 6mmBR, .243 Win, 6.5×47 Lapua, 6.5 Creedmoor, 6.5×55, .308 Win, 30-06, or .338 LM 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. [Editor’s NOTE: The original test was conducted in 2008. The velocity of current-production Lapua factory ammo might be higher or lower, so your results may vary.]
When you complete a new 6mmBR rifle, it’s definitely smart 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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After Norm Harrold won the 2018 F-Open National Championship in Raton, New Mexico, setting a new 1000-yard National Record in the process, many of our Forum members wanted to see Norm’s championship-winning rifle, and learn more about Norm’s experience at the Nationals. Read on for coverage of Norm’s equipment and .284 Shehane ammo. Scroll down and you’ll find a detailed video showing how McMillan builds the advanced Kestros ZR stocks, like the one Norm used at Raton.
Norm posted: “I made it home from Raton 2018 F-Class Nationals and what an unbelievably amazing week I had. I was blessed enough to bring home a new F-Open 1000-yard record and the National Championship! Our Team McMillan took second in Mid-range and fourth overall in Long Range. I am so thankful and blessed to have this opportunity and to be able to do it with such a stand-up group of competitors and lifelong friends. Thanks to all our sponsors: McMillan Fiberglass Stocks, Nightforce Optics, Kelbly’s [Actions], Bartlein Barrels, and Berger Bullets.”
Gun and Load: Norm’s F-Open rig features a McMillan Kestros ZR stock and Bartlein barrel chambered for the .284 Shehane, which has a bit more case capacity than a standard .284 Winchester. Norm loaded Berger 184gr 7mm bullets in Lapua brass. Norm revealed his load in an Erik Cortina YouTube Video. Fellow shooter Erik Cortina joked — “the minute this video goes live, the 184s will be hard to find”. Norm says “Stock up guys — they shoot good!”
Here Norm Harrold shows his shooting form. Note how low the McMillan Kestros ZR forearm sits on Norm’s SEB NEO front rest. Norm also uses a large footprint rear bag for enhanced stability.
Harrold Shoots 200-22X to Smash 1000-Yard F-Open Record
On a rainy day at Raton, Norm shot brilliantly to set a new F-Open National Record: 200-22X at 1000 yards. (The previous record was 200-17X.) How could he get 22 Xs for a 20-shot string? Under NRA rules, if you shoot all Xs for the full string, you are allowed to keep shooting for as long as you can put shots in the X-Ring. Norm almost missed the chance to extend his X-Count. After his 20th shot, Norm recalled, “I said ‘I’m done, give me my target’, but … my shooting partner said ‘No! Keep shooting!’” So Norm did, drilling two more Xs to set the new National Record.
Kelly McMillan Shows Design and Construction of the Kestros ZR:
In this video, Kelly McMillan explains the design features and construction methods for the Kestros ZR, a fiberglass Kestros with aluminum extension rails in the front. Kelly explains “how and why we made the stock the way we did” and he shows how to retro-fit standard Kestros stocks with the new front rails. On the ZR the rails are anchored to a reinforced area for extra rigidity. In addition, the cantilevered rails are milled to be perfectly parallel. If you shoot F-Class we strongly recommend you watch this video.
Kelly McMillan showed us the prototype Kestros ZR at the 2018 Berger Southwest Nationals.
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A popular feature of our Shooters’ Forum is the long-running Pride and Joy thread. There you’ll find photos and descriptions of dozens of interesting rifles — from rimfire rigs to big-bore boomers. Forum member Ryan M. (aka “Dieselgeek”) posted a handsome .260 Remington tactical rifle built by Short Action Customs in Wellington, Ohio. The rifle features top-of-the-line hardware. The coated, stainless Alpha 11 action (from Defiance Machine) carries a Bartlein M24-contour 26″ barrel with muzzle brake. The stock is a thumbhole T5A from Manners Composites, fitted with APA bottom metal for AW magazines. On top is a Bushnell ERS 3-21x50mm scope with G2 reticle. Riding on an under-mounted rail is an Atlas bipod with quick-release lever.
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!):
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.”
Have you ever wondered how a cut-rifled barrel is made? This 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.
Read About Cut-Rifling Process at Border-Barrels.com
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.
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 Koble continues to work for Border Barrels, which maintains operations in Scotland.
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Steven Blair’s recent report on the .300 WSM for F-Class stirred quite a bit of interest. If you’re a serious F-Open competitor, you’ll definitely want to read that article, which covers the pros and cons of the .30-Cal WSM loaded with the ultra-high-BC 230gr Berger Hybrid bullets.
If you’re thinking about building a .300 WSM for F-Class, here’s a rig that can give you some design and hardware ideas. This eye-catching custom .300 WSM F-Open rig belongs to Forum member Keith T. (aka “KT”). With its striking “bumblebee” color scheme, it will certainly get noticed on the firing line.
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Bold Bumblebee .300 WSM for F-Class
Forum member Keith T. (aka “KT”) just got his hands on his new .300 WSM for F-Class and long-range competition. It’s a handsome brute, decked out in a “bumblebee” (yellow and black) laminated stock. Keith’s rifle features a Defiance Machine Deviant Long Magnum action (with Jewell trigger) in a Precision Rifle & Tool (PR&T) F-Class Lowboy stock. Keith has two 30″-long, 1:9″-twist barrels for the gun, one made by Brux Barrels, and the other by Bartlein. Both barrels have identical .300 WSM chambers cut with the same reamer. Keith will test both and then use the best-performing of the two in competition. Riding on top is a Nightforce 12-42x56mm Benchrest Model scope. All the work was done by Accurate Ordnance (AO), based in Winder, Georgia.
Keith reports: “This one took a while to get built due to parts availability issues, but I’m glad it’s done! Thanks to Accurate Ordnance and Nightforce and all their help.” NOTE: Accurate Ordnance tells us that a rifle like this can normally be completed in 6-8 weeks, once all key parts are in hand.
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In most of the country “March Madness” is all about hoops. But in the Sacramento (CA) area, “March Madness” is a popular multi-match shootfest that brings out some of the top F-Class and sling shooters in the region. During this year’s Folsom Shooting Club March Madness series, Forum member Bob A. (aka “Killshot”) brought out his “Forum Classifieds Special” and beat all comers in the F-Class Division in both the American-Canadian Match and the Long Range Regional Match (See Results). Bob’s 6mm Dasher sports a blue-printed Rem 700 action. Who says you need a high-dollar custom action to run with the big dogs? In fact, this same gun, built with components sourced from Forum Classifieds, set a Sacramento F-Class range record of 200-17X. In this story, Bob talks about the build, and he explains his methods for loading ultra-accurate Dasher ammo.
Bob’s Budget-Build Dasher F-Classer
I’m a newcomer to F-Class competition and shot my first match in 2010. After getting accustomed to the match format and seeing what others were using, I wanted to build a proper rifle for F-Open but needed to keep it simple and, well, cheap. I found a solid “base” to build on in the form of a Dave Bruno-built, “pre-owned” 6-6.5×47 Lapua that I located in the AccurateShooter Forum classifieds in late 2011. The base action was a trued and blue-printed Remington 700 receiver circa 1971 with a spiral-fluted bolt. It was in a Shehane ST1000 stock painted sky blue and had a Jewell 1.5-oz BR trigger. I sent the bolt to Greg Tannel (Gretanrifles.com) to have the firing pin hole bushed and sleeved, the ejector removed and the hole filled and the face trued. I ugraded to Tannel’s Light Steel firing pin assembly while it was out.
Having the working bits completed, I needed a barrel. So I went to the AccurateShooter classifieds again and found a 1:8″-twist, 30″ x 1.25″ (diam.) Bartlein with a 0.236″-land bore. I called Dave Kiff and explained my pursuit and he recommended his PT&G “world record” 6 Dasher reamer (.2704″ no-turn neck and .104″ freebore). A month or so later the reamer and gauges arrived.
I had the barrel chambered by Marc Soulie of Spartan Precision Rifles (510-755-5293, Concord, CA). Marc is a great builder and I’m pleased to call him a friend. He is an outstanding shooter himself and developed his lathe skills from several “name smiths” I won’t mention here, all while he continued in his previous profession. Marc went into building custom rifles full-time a couple of years ago and is at the point in his career that word of his work has spread. He was recently selected by Frank Galli to create 25 rifles, each customized to the buyer’s specs, for the Sniper’s Hide 2013 Group Build. Marc has also built a number of tactical-style rifles for the Northern California Practical Precision Rifle Club’s shooters, several of whom have won or placed high in major matches.
After his great shooting in March, Bob reports: “I could not be happier with my little budget build. With a few more good scores I might even stop looking at BAT Machine’s website — my little old Remington action seems able to hold its own with the BATs and Kelblys just fine.
The rifle got its good looks from a Pennsylvania artist named Kenny Prahl. His Prahl Designs shop (724-478-2538) added the white ghost-flames over the existing sky blue metallic paint. Kenny’s work with an airbrush floored me, he does everything from stocks to mailboxes to gas tanks equally well.
“I use a Nightforce Benchrest 12-42x56mm with a NP-2DD reticle. To help my aging eyes I use a 3.5X BulzEyePro lens booster, I found it helped with mirage and target clarity enough that I rarely dial down the magnification even when mirage is bad.”
Looks Great, Shoots Better
Fire-forming showed great promise — ten-shot groups of half an inch at 200 yards were typical. I lost only one case to a split neck and the “blow lengths” are good and consistent.This was followed up with load development which saw 100-yard, five-shot groups in the .1s and .2s as the rifle showed its preference for Reloder 15 over Varget powder, and for CCI 450s over all other primers. The bullet of choice is the ever-popular Berger 105gr Hybrid Target.
In February 2012 I began shooting the Dasher in monthly club matches at the Sacramento Valley Shooting Center, the home range of a number of excellent F-Class, Benchrest and High Power shooters. Using a Farley Coaxial rest up front (also picked up from a WTB ad on AccurateShooter’s Forum) and an Edgewood bag in the back, I gradually improved my gun-handling to the point where I could shoot a respectable score. This was very different from the bipod shooting I’d done in the past in F/TR.
Like many others, I settled on the high-node dose of Reloder 15. Shooting F-Class puts a good number of rounds down the tube in a short time-frame. That can be hard on throats. At roughly the 1,200-round mark the groups started to grow as the throat wore. So, a barrel set-back was needed. The barrel was rechambered by another great California gunsmith, Ken Breda (831-334-2386, Aptos, CA). Ken, a sling shooter and all-around good guy, was able to get me back shooting with little down-time. When I went back to the range, I found the now 1.25″-shorter barrel shot equally well, even with the same load I had previously used.
An October Surprise — New Range Record, 200-17X
The chamber setback and muzzle cleanup brought the Dasher back to life and it was was really shooting well with several “cleans” shot at a few distances at club matches this summer. I shot the Folsom Shooting Club’s October match, this one a 3×600. I drew relay number two and settled in to spot and score for the shooter who drew relay one. The wind was very light and good scores were being posted. I set up for my first string and fired four sighters: three 10s and one X.
“Here we go”, I thought as I went for record. Happily, the first six shots found the X-Ring before a 10 came up out of the pits. The next six shots also found the X-Ring, then another 10 came up. Shots 15 thru 19 were all Xs and I finished the string of twenty shots with a final 10. I’d cleaned the 600-yard F-Class target with 17 Xs! This was by far my best “clean” at any distance.
I followed the first string up with a 199-6X and a 195-7X as the wind was beginning to harrass everyone on their third strings. My final score of 594-30X gave me my first win in F-Open by one point. I was very happy and received many congratulations from fellow shooters after the match. It wasn’t until I arrived at the range for November’s match that I learned that my 200-17X was a new range F-Class record.
I couldn’t believe it. Considering the quality of shooters and the number of big matches held at Sacramento Valley, setting a range record of ANY type there is an accomplishment. I have been fortunate to meet and shoot with some absolutely fantastic people at the Sacramento Valley Shooting Center. It took a little while to find out just how talented some of them were — several are national champions and record-holders but you’d never know it talking to them. These guys have always been helpful to others. Likewise, I try to help out when new shooters need a hand.
Dasher Loading Tips
My chamber is set up for Lapua’s current iteration of 6mmBR brass, in the blue plastic boxes. My case preparation is straight-forward. I fire-form with virgin cases right out of the box. I don’t size them but I will give the primer holes a good look and clean up the flash hole with a .058″ bit in a pin vise. To fire-form, I seat a Berger 108gr BT .030″ into the lands over a standard 6mmBR load of Varget.
For my match load, I use Alliant Reloder 15. We shoot year-’round in Northern California. It was a brisk 28º at the start of our January match this year. Your load needs to be able to carry you from that cold to the 100º+ heat we get in the summer months. While Varget is less sensitive to temperature changes, RL15 gives me lower spreads and better long range control.
I clean my fired cases with stainless steel media in a Thumler’s rotary tumbler after every firing. I anneal after every other firing using a Bench-Source machine which is very well made and easy to operate. I use a Whidden full length bushing die with Redding bushings for sizing.
After sizing, I chamfer the inside of the neck with the K&M tool which has a pilot rod centered in the flash hole. Then I’ll give the neck and mouth a “once over” with some 0000 steel wool. I finish loading off with a Redding Competition Seating Die with the micrometer top.
I use a carbide ball on the expander rod of the full length sizing die. I use a .266″ TiN-coated bushing and the ball just kisses the inside walls of the sized neck. I get very consistent neck tension this way and have had no issue with split necks.
Seating Depth Considerations
With fire-formed brass, the junction of the bullet’s bearing surface and boat-tail is above the neck/shoulder junction of the case, so I have no issues with donuts. You can see how a loaded round looks in the photo at left. For occasional trimming, I use a very nice little Possum Hollow trimmer that indexes on the case shoulder.
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Barrel Velocity Variance
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“Here we go”, I thought as I went for record. Happily, the first six shots found the X-Ring before a 10 came up out of the pits. The next six shots also found the X-Ring, then another 10 came up. Shots 15 thru 19 were all Xs and I finished the string of twenty shots with a final 10. I’d cleaned the 600-yard F-Class target with 17 Xs! This was by far my best “clean” at any distance.
Dasher Loading Tips
I use a carbide ball on the expander rod of the full length sizing die. I use a .266″ TiN-coated bushing and the ball just kisses the inside walls of the sized neck. I get very consistent neck tension this way and have had no issue with split necks.
