August 16th, 2014

Radical Gain-Twist Barrel for AR and High Power Rifles

“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.

Twist Rate

Erik Dahlberg illustration courtesy

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