Comments on: Radical Gain-Twist Barrel for AR and High Power Rifles

By: Dan Shinn

Dan Shinn — Fri, 12 Jun 2020 19:41:29 +0000

You should look into the application for gain twist rifling in small bore artillery. I worked for company that at one time was the largest manufacturer of automatic cannon in the world. We built all of our weapons using gain twist rifling to get the added velocity without twisting the spin rings off of the projectiles.

By: Jerry Ward

Jerry Ward — Sun, 17 Jan 2016 19:39:40 +0000

Actually, I thought that I invented the progressive-twist barrel in my waking moments this morning, so I Googled it, and I was immediately disappointed and intrigued at the same time when I came across this article. Okay, so I wasn’t the first person to come up with the idea, but maybe my motivation is somewhat different. My rationale for a gain-twist barrel was more about friction and heat reduction. My thought was that most of the bullet etching occurs at the chamber end of the barrel as the bullet first engages the rifling. And, I thought, why not reduce the friction at the beginning of the bullet travel by starting with completely straight lands then start the rotation and gradually increase the twist until it hits the target rate of twist just before exiting the muzzle. This way most of the etching occurs before twist is imparted to the projectile; the bullet has full purchase on the barrel before the twist begins. As a simile, think of a bobsled run. The sled starts out slow out of the gate then accelerates in a straight-away before engaging the first turn in the track. As the sled continues down the steep track, acceleration due to gravity is resisted by centripetal friction on the runners, yielding an optimal speed and turn ratio. Yes, I just made this up, but it makes sense to me. What do you think?

By: Eric B.

Eric B. — Thu, 20 Aug 2015 01:32:50 +0000

“Bore squeezing” (swamped barrel) helps mostly in .22 caliber cartridges in extreme cold weather.

Olympic Biathalon rifles in .22 LR absolutely MUST be “bore squeezed pre-” if they are to be accurate at, say, minus 10 F. and lower.

I witnessed this as a Nordic ski patroller in the1979 Lake Placid Winter Pre-Olympics. The temperature in the first morning at 8 AM was -20 F. and officials waited until the temperatures were -10 F. to begin the events for safety reasons. Those with Austrian and Russian rifles shot the best BECAUSE they were the only ones making “bore squeezed” barrels. In those days nobody else understood the effect of having that kind of barrel! Remington, who tried to produce accurate biathlon rifles had given up before the games.

By: Eric B.

Eric B. — Thu, 20 Aug 2015 01:24:08 +0000

I would like to have a replacement barrel (in about a year or so) for my Ruger Precision Rifle in 6.5 Creedmoor.

The RPR factory barrel comes with a standard 1:8 twist. I think a MODERATE gain twist (T-Twist or Transitional Twist) in a 24″ barrel from 1:10 to 1:8 would likely not create any bullet jacket “skidding” deformation but tend to help accuracy. I do not know how much velocity gain I could get from that twist rate-of-increase but I’ll bet Bartlein Barrels does.

Replacing Ruger’s very good 5R barrel with a great 5R custom barrel would make that rifle the equal of the most expensive long range rifles, especially with a trued breech and bolt head.

By: John

John — Sun, 24 May 2015 08:18:34 +0000

How does Barlein Barrels this compare with the Arms-tech polygonal progressive gain twist barrels?

Also what do you think of Colt Canada/Diemaco with them bore squeezing their barres?

Have you ever though of trying a cryoed polygonal gain twist bore squeezed barrel?

By: Ben

Ben — Tue, 17 Mar 2015 20:48:50 +0000

Nevermind, my own numbers show me why I am wrong. While it is true that it moves the wear down the barrel, because bullets do accelerate so fast in the first inch or two, the torque on the bullet is highest there as well.

By: Ben

Ben — Tue, 17 Mar 2015 20:39:31 +0000

The problem I have with the idea of gain twist is that it seems to only make sense if the bullet is traveling a constant velocity from the chamber to the muzzle or was slowing down. Instead, the bullet engages the lands when it is practically at rest and increases its spin proportionally it increases in velocity down the bore.

Gain twist poses a problem because from the chamber end (low velocity) to the muzzle end (high velocity), the twist rate also increases, meaning two factors that are imparting much more torque than the bullet would have otherwise experienced.

If at, say, 5″ from the muzzle, the bullet is moving at 1100 fps, but at 20″ from the muzzle, it is moving at 3000 fps, in a constant 1:9 twist barrel, the bullet would have to spin up from from 88k RPM to 240k RPM in that 15″, or a difference of about 172k RPM. In a gain twist going from a 1:15 twist to a 1:9 twist, with the same acceleration, it would be spinning only 53k RPM at 5″, or have to increase a difference of 187k RPM in that same 15″.

Without even including the issue of the angle of the rifling changing to get gain twist also severely deforming the bullet (effectively swaging it in an inconsistent way), the increased friction, wear, and fouling caused by the increased forces on the bullet/rifling to account for the increased torque makes this seem like a very bad option.

By: Will

Will — Thu, 01 Jan 2015 02:29:00 +0000

As a biology/physiology student with a HUGE passion for physics (and shooting), I Google’d this progressive rifling idea unaware it already existed. Concepts of angular momentum is critical to the rotation of the bullet. By rotating the bullet in relation to it’s acceleration, and gradually increasing it’s spin, will result in less resistance against the lands, thus less lead deformity. Also, less rifling resistance/friction allows the bullet to accelerate forward faster unimpeded. Now all I need to do is finish school (next year) and buy one of these $400 barrels…..

By: Todd

Todd — Sat, 27 Sep 2014 11:15:50 +0000

Can anyone provide contact information for Mr. Carlos? I am interested in speaking to him about a build. I like his train of thought on this and his use if 90gr bullets.

Thanks
Todd

By: Fred Melzer

Fred Melzer — Tue, 19 Aug 2014 16:56:31 +0000

A few years ago I tried a 7-mm barrel with a progressive twist. The starting twist was 1-19″ and the ending twist 1-11.25. The barrel had cut rifling, but was not lapped. The barrel maker told me that his barrels are smooth enough and did not need lapping and recommended regular break in. The barrel fouled up badly whether from the twist or the lack of lapping, I don’t know?

Some mathematics revealed that the engraved land would widen on the bullet forward side of the bullet shank by something like 0.005″. When you multiply that by six grooves, that metal has to go somewhere. I exchanged the barrel for a standard 1-11″. Progressive twist barrels are advertised and claim superior accuracy? At the time I did not know about the Micro Hone process, this would have helped to find out whether the progressive twist barrels are really more accurate.