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August 16th, 2014
“Gain-twist” refers to a form of barrel rifling where the twist rate gets tighter over the length of the barrel. For example, a gain twist barrel might start with 1:12″ twist and finish with 1:8″ twist. There is some evidence that gain-twist rifling can deliver more velocity (compared to a conventional barrel) with certain cartridge types. There have also been claims of increased accuracy with some types of bullets, but such claims are more difficult to quantify.
Gain-twist rifling is not new. This form of rifling has been around for a long, long time. The first gain-twist barrels appeared in the late 1800s. However, in the last few years, there has been increased interest in gain-twist barrels for both short-range and long-range competition.
Video Explains Gain Twist Rifling
Radical Extreme Gain Twist Barrel Design
In this video from our friend John M. Buol Jr., gunsmith John Carlos talks about a fairly radical gain-twist barrel design for high power and service rifle shooters. Produced by Bartlein Barrels, this gain-twist barrel starts with a 1:14″ twist and finishes with a 1:6.8″ twist at the muzzle (See 1:50 time-mark). Carlos believes that this type of barrel delivers higher velocities while providing excellent accuracy for a wide range of bullet weights. In .223 caliber, the gain twist works with the 75-77 grain bullets used on the “short course” while also delivering excellent accuracy with the longer 80-90gr bullets used at 600 yards and beyond. Velocity is the important bonus for long-range use. Carlos says the gain twist barrels deliver greater muzzle velocity, allowing a 90 grain bullet to stay well above the transonic zone, even at 1000 yards. (See 4:50 time-mark.)
This 1:14″ to 1:6.8″ gain-twist barrel is the product of much experimentation by Carlos and Bartlein. Carlos states: “We’ve varied all sorts of internal dimensions, such as the land height, and the groove depth. We’ve tried 5R rifling and 4-groove rifling, and we’ve worked with various rates of twist, and I believe we have it down really well right now.”
In this video, John Carlos explains the history of gain-twist rifling, and he explains how modern Bartlein gain twist barrels have been developed in recent years for both benchrest and High Power applications. If you are interested in barrel technology and design, take the time to watch.
Erik Dahlberg illustration courtesy FireArmsID.com.
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August 2nd, 2014
 Brux Barrels, based in Lodi, Wisconsin, has earned a reputation for producing great-shooting tubes. Brux-made barrels have won their fair share of matches, and set some notable records in the process. Last year, Rodney Wagner shot the smallest five-shot, 600-yard group (.0349″) in the history of rifle competition, using a Brux barrel chambered for the 6mm Dasher.
Folks often ask us why Brux barrels shoot so well. “What’s the secret?” they ask. We can only answer with what Brux explains on its own website: “To make a cut-rifled barrel you have to start off with the proper ingredients: the best steel available, skill, and experience. Since there are really only two main suppliers of barrel-quality steel, the skill and experience is what really makes a barrel maker stand out.” Here is how Brux’s co-owners, Norman Brux and Ken Liebetrau, explain all the procedures involved in making a Brux cut-rifled barrel:
| Brux Barrel-Making Process, Start to Finish
We start out with either 4150 chrome-moly or 416R stainless steel double stress-relieved bar stock. The bar stock starts out at 1-9/32″ in diameter and 20-24 feet long so we cut it to length.
Step two is to rough-contour the outside of the barrel blank in a lathe.
Thirdly, the blank gets mounted into a Barnes gun drill. The cutter bit has holes through which oil or coolant is injected under pressure to allow the evacuation of chips formed during the cutting process. This is called “oil-through” or “coolant-through”. Without this, you wouldn’t want to even attempt drilling a hole 30” long and under ¼” in diameter. The combination of a 3600rpm and good flushing allows us to drill a beautifully straight and centered hole .005” under “land” diameter at a rate of 1” per minute.
Clean the barrel.
Next the blank is sent back to the lathe to machine the finished contour of the outside.
Clean the barrel again.
Now, the blank is sent on to the Pratt & Whitney reamer in which an “oil through” reaming tool is used to cut away the extra .005” left in the drilling process. The reamer makes an extremely accurate bore size and after it is finished the bore will have a better surface finish and will be at the proper “land” diameter.
Clean the barrel again.
In the sixth step we hand lap each barrel to remove any slight tool marks that may have been left by the reamer and inspect every one with a bore scope. If the barrel doesn’t meet our standards for surface finish and tolerance it doesn’t get any further.
Clean the barrel again.
The barrels then go onto the rifling machine which is responsible for cutting the all so familiar grooves in the bore. A caliber/land configuration-specific rifling head is used to progressively shave away small amounts of steel to form the rifling grooves. This is accomplished by simultaneously pulling the rifling head through the reamed blank as the blank is spun at a controlled rate. After each cut, the blank is rotated 90 degrees (for a four-land configuration) and after one full rotation (360 degrees) the rifling head is slightly raised to shave off the next bit of material. This process is repeated until we reach groove diameter.
Clean the barrel again.
Lastly, the barrel is hand-lapped again (to ensure a smooth bore), and a final inspection is performed with the bore scope.
The barrel is cleaned one last time, wrapped, packed, and shipped to [the customer]. |
Anyone reading this detailed description of the Brux barrel-making process will doubtless come away with a new appreciation for the time, effort, and dedication required to produce a premium match-grade cut-rifled barrel. Obviously, there are no easy shortcuts and great attention to detail is required each step of the way. As shooters we’re lucky that we have barrel-makers so dedicated to their craft.
Credit James Mock for steering us to this Barrel Making 101 feature on the Brux website.
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April 24th, 2013
This story first appeared last year. We’re featuring it again by popular request.
Some of our mechanically-skilled readers chamber their own barrels or bed their own stocks. But these are relatively simple tasks compared to the jobs of constructing an entire rifle plus building an advanced front rest from scratch. Well that’s exactly what Forum member Steve B. (aka Essexboy) did. He built his own rifle and an impressive twin-belt-drive pedestal rest. (Click photo below to see large version). And get this, Steve’s home-made rifle was victorious in its first-ever match. Steve reports: “I shot my first Comp with the rifle this weekend and managed to win with a score of 239-21!” (The match was shot at 300/500/600/1000/1100 with English scoring of 5 points for center bullseye).
Do-It-Yourself F-Open Rig from England
Steve, who hails from Essex in the UK, constructed virtually every component of his skeleton-style rifle except the 28″ HV Bartlein barrel (chambered as a 6mm Dasher) and the Tikka 590 donor action. Steve also did all the design and fabrication work on his one-of-a-kind front rest. Steve tells us: “Over the last year or so, I made this rifle stock and rest. I managed to make it all on a little Myford Lathe, as you can tell I’m no machinist but it saved me a load of money — so far I’ve got about $200 invested plus the barrelled action. The stock is aluminum except for the stainless steel bag runner. The rifle came in at one ounce under weight limit for F-Class Open division.” Steve did get help with the chambering and barrel-fitting, but he hopes to do all the barrel work himself on his next project.
 The gun is very accurate. Steve notes: “I have shot the rifle to 1100 yards and it shoots well. Last time out the rifle dropped just one point at 1000 yards and 5 points at 1100 yards [English scoring system]. I know it’s not pretty, but it got me shooting long range F-Class for peanuts.” Message to Steve: Don’t worry how it looks. As another Forum member observed: “Any rifle that shoots well at 1100 yards is beautiful….”
Steve started with a Tikka 590 action: “The whole stock was made on a small (6.5×13) lathe and a vertical slide. This caused a few head scratching moments, figuring out how to hold the T6/HE30 alloy for the milling/turning operations, but it did teach me a few things. The hardest parts were clamping the longer sections (such as the fore-end) and keeping it all square. Due to the short cross-slide travel I had to keep re-setting the parts. I managed to keep all measurements to .0001″ (one thousandth). I’m most proud of the trigger guard (photo below). This took a full day but came out really well, even if I say so myself.”
Belt-Driven Front Rest
We’re impressed with Steve’s ingenious front rest. Steve explains: “The rest is belt-driven and still in the experimental stage — hence no powder coating or polishing yet. I may have gone over the top as the key moving parts (the pulleys) run on three (3) types of bearings: radial; reamed bush; and a ball race. The main post runs on a radial bearing and the feet even have bearings in them, so when I raise the main body up (for rough height adjustment) the foot stays static.”
Will Steve build another rifle? Steve says he will, and he’s upgraded his tools: “Since building the rifle I have acquired a bigger lathe (Harrison m250) and a milling machine. For the next project I hope to be able to do the barrel work (threading, chambering, crowning) as well.” The next gun might be another Dasher. Steve explains: “After extensive reading on AccurateShooter.com, I chose the 6mm Dasher chambering, as I have a shoulder problem and can’t shoot a rifle with a lot of recoil.”
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April 11th, 2012
After we ran our Bulletin news item about Ron Boyd’s amazing 1.462″ 5-shot group at 1000 yards, many readers wanted to see some close-up photos of Ron’s rig. Thanks to Robert Ross of the MidWest Benchrest Club, we have some photos of Ron with his ultra-accurate 6mm Dasher 17-lb Light Gun. This rifle features a BAT SV action, Precision Rifle & Tool (PR&T) “Hammerhead stock” with 5″-wide front wings, Nightforce 12-42 Benchrest scope, and Jewell trigger. Ron had just added a 30″ 1:8″-twist Bartlein barrel to the gun before shooting the 1.462″ group. That barrel only had about 40 rounds through it when it produced the near-record group. The barrel in photos below was a 28″ Benchmark, recently replaced with the new Bartlein. Ron’s ultra-accurate 6 Dasher load consists of surplus Long Range Match powder, with Spencer 103gr bullets. Ron also anneals his Dasher brass after every firing.
CLICK Small gallery photos to view full-size images
Henry Pasquet’s .284 Win Heavy Gun
At the same Midwest Benchrest Club IBS match where Ron shot his small five-shot group, Henry Pasquet drilled a very impressive 3.348″ ten-shot group. This group was just .304″ off the IBS 10-shot Heavy Gun record of 3.044″ shot by Joel Pendergraft in 2009. We are told that Henry was running a straight .284 Winchester. You can see in the inset photos below that Henry uses a tuner on his barrel. He also has fitted an extra-wide front sled and a machined rear “keel” to reduce torque and improve tracking. Henry can adjust windage and elevation with BOTH his Fulghum front rest (from Randolph Machine) and his adjustable rear rest.
CLICK Small gallery photos to view full-size images
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