Home Forums Hunting & Shooting Ask The Gunwriters Gain twist barrels: what rate of gain to ask for?

I talked with a nice and helpful fellow at Bartlein when I ordered a gain twist barrel in .338 and he recommended a very limited gain in the twist on the order of a gain of one to two inches over the length of the barrel.
It had always seemed to me that quite a bit of gain would be ideal, i.e., for a 6mm barrel having a 7.5" twist at the muzzle but starting the bullet at a very easy twist rate of say 1 in 14 inches. ( I hope I am stating this clearly.)
Any opinions or experiences are appreciated.

My thoughts: Drastically changing the twist from the throat to the muzzle is going to drastically change the geometry (pitch angle) of the rifling, which is going to dramatically mangle the surface of the bullet. Seems like it would hinder accuracy more than aid it at a certain point.

I Don't think a gain twist is worth doing. It's going to increase the rifling distortion which is going to effect BC

I am not convinced a gain twist barrel is any benefit. If you think about it, a bullet starts from zero as it starts into the rifling then gains speed thus rate of rotation as it goes through. Altering the twist requires that the engraving on the bullet also changes. I have no data to back my conjecture but I have never seen any data to support the idea.

Experiments have proven a gain twist does NOT reduce initial, peak pressures much, if at all--which is the most common supposed benefit. Instead the early pressure peak is caused by the bullet hitting the rifling, which requires considerable force to engrave the bullet.

Another point: If gain-twist rifling had substantial advantages over standard rifling, top competitive shooters (whether short-range benchrest or long-range target) would be using them. I don't know of any who do, and I know some top shooters in several disciplines.

The Germans believed it had some applications for artillery in WWII but even there I don't think it is used much. I know some rifling operations don't produce a true twist but don't think any change the length of the bore unless something is set up wrong. A mild gain twist of an inch or less should not hurt accuracy. But it is doubtful of any other gains so why do it?

Gain twist has a place but I rather think not with modern arms. If shooting large soft alloy lead bullets a measured acceleration allows the bullet to achieve sufficient rpm to avoid stripping. It does serve the objective well. Likewise if shooting very heavy projectiles using drive bands a gain twist would be beneficial. Apparently the Navy thought so anyway as some of the old ship guns had gain twist....and a lot of grooves.



Their max weight for a 16" shell was 2,700 pounds with MV of 2500 to 2690 fps. I have seen pictures of this where it is quite obvious they had gain twist but cannot find any at present.

"Kills on both ends."

My preference is for a moderate gain (25% or so) but I have a couple which gain a lot (24 to 8 in one 6.5mm, 30 to 12 in a 25) and both shoot very well. The truth is though, I think the gain twist is a novelty as much as anything. The only reason I have them is because the maker likes making them because Harry Pope made them that way! GD

Yep--and Pope liked them for lead bullets, due to not deforming bullets as much during their initial engraving. But lead bullets are also more malleable than jacketed bullets, thus more resistant to meaningful deformation.

Pope was a very interesting guy, far more educated in basic physical principles, due to going to M.I.T. But like a lot of visionaries, he had a hard time making a living....

Rock Creek barrels are gain twisted. They have been for years even before the advertised as such. I have had exceptional luck with their barrels too.

Come on, guys. It's gotta be good - it was used in Mannlicher-Carcanos.

A slight gain twist seems to be popular with prs shooters but whether there is any advantages remains unclear.

Am sure, knowing the tendencies of competitive shooters, that if somebody won a major PRS match with a gain-twist barrel, then a bunch of others would be using them.

But as I mentioned earlier, I know a few very good competitive shooters. On is a local friend who set the 1000-yard benchrest record for the smallest 10-shot group at 1000 yards (under 3 inches both times), and he does not shoot gain-twist barrels.

Another set a world record in "short range" benchrest shooting maybe 3-4 years ago. Same deal.

As far as I know David Tubb does not use gain-twist barrels, but could be wrong. However, if he does my searches on his website for various kinds of info has not found that.

Hello Mule Deer and All

I am curious if there might be an advantage here where someone just needs a faster twist to stabilize a heavier/longer bullet such as a 150 gr .270 and then go to a 170 gr spitzer.
What does every think about this idea?

Also, what does everyone think about of just screwing on an extension giving a faster twist to be able to stabilize longer bullets. This might be a off the wall question...BUT STILL!

Glenn

I think if you want to shoot a longer bullet that won't be stabilized in a standard twist, you have a faster-twist barrel chambered for your cartridge and screw it onto your action. You can't speed up a twist that already exists by twisting the end of the barrel or something.

I imagine it is possible to create a gain-twisted barrel extension, but I imagine the results would suck so much that it would be better to just get a new barrel and swap between them, which is pretty simple, actually. You could align the rifling in the gain-twisted extension, but pressure and vibration and the need to have the thing stay tight would mean that it would likely eventually get out of alignment.

I think that would have all the questions of an (abrupt) gain twist, along with the machining difficulties of precisely lining up two bores and two sets of threads.

There is a lot of talk about deformation of bullets by gain twist barrels and the truth is, all rifling deforms bullets. A recovered bullet, fired from a gain twist barrel, is identifiable because the groves in the bullet are slightly wider at each end. This is more noticeable if the rate of gain is significant. In the end, as I've said before, gain twist barrel shoot neither better nor worse than a uniform twist barrel if the quality in other aspects is equal. Just like the number of grooves or rifling configuration, it is a novelty (although five groove barrels can be problematic when chambering).
One area where the gain twist does have a following is in the Shuetzen competitions. Of course, they are shooting lead bullets. GD

A few years ago several of the benchrest shooters were using gaintwist barrel's but the gain was very slight. If I recall one of my friends was shooting a 1-14.25"to 1-13.75" at the muzzle, they seemed to work quite well but I don't know of anyone still using one

Do you know what the goal was for such a small increase in twist? Does it keep pressure up better going down the bore or something because of slight engraving change in the bullet? I'm just guessing.