Gain rifling

[Bullshop Junior]

Something I just recently learned about it gain rifling. Has anyone ever played with this? How does it effect accuracy, especially with cast?

[texassako]

A lot of the 6.5mm Carcano rifles are gain twist. The Italians thought it helped to gradually increase the twist in the early days of smokeless powder to prevent damage to the bullet. It doesn't seem to be worth it to me in this instance. I have been working up cast loads in 2, one gain twist and one not, and the non gain twist rifle is shooting better and even shoots the infamous Cruise Missile all right.

[Southpaw 72]

Not a rifle but I believe the SW x frames in .460 are a gain twist as well. I've heard nothing but good things from them in terms of accuracy.

[Bullshop Junior]

The rifle I was looking at with gain twist was a AR15

[aspangler]

The rifle I was looking at with gain twist was a AR15
Could you post a link to that?

[Bullshop Junior]

It was a S&W MP15. The fella at the gun store told me that it has the R5 style rifling and gain twist. I havn't actually looked up the specs online. I was just wondering how the concept worked.

[Artful]

S&W MP15 Sporter? - the 1:8? or the 1:9?

from boot's obermeyer web site
What does it mean when a barrel is said to be a "5R"?

5R is the form of rifling I developed for use in most target barrels and in many sporting barrels.
These barrels have 5 grooves, and the lands have angular sides. I have observed that bullet jackets will deform such that they remain closer to the R-form lands than they will to the sharp-edged lands present in conventional-style rifling. This reduces powder fouling at the corner of the grooves. The angled form of the lands also helps to reduce jacket failures in quick-twist barrels.


http://obermeyerbarrels.com/faq.html

https://precisionrifle.files.wordpress.com/2014/10/5r-barrel.jpg

Gain-twist rifling begins with very little change in the projectile's angular momentum (http://en.wikipedia.org/wiki/Angular_momentum) during the first few inches of bullet travel after ignition during the transition from chamber (http://en.wikipedia.org/wiki/Chamber_%28firearms%29) to throat. This enables the bullet to remain essentially undisturbed and trued to the case mouth. After engaging the rifling the bullet is progressively subjected to accelerated (http://en.wikipedia.org/wiki/Accelerate) angular momentum (http://en.wikipedia.org/wiki/Angular_momentum) as burning powder propels it down the barrel. By only gradually increasing the spin rate, torque is spread along a much longer section of barrel, rather than only at the throat where rifling is eroded through repeated rifling engagement.

http://lutzmoeller.net/English/Rifle-barrels.php
http://lutzmoeller.net/Waffen/Bilder/Progressivlauf.jpg
Gain twist rifling was used as early as the American Civil War (http://en.wikipedia.org/wiki/American_Civil_War) (1861-65). Colt Army and Navy revolvers both employed gain twist rifling. Gain twist rifling, however, is more difficult to produce than uniform rifling, and therefore is more expensive.

[country gent]

Theroretically the twist starts at a very slow rate and increases to a faster twist or full rate. Its has several advantages 1) is that it helps to alieviate bullets stripping in the rifling, 2) the bullet supposedly seals better the full trip down the barrel as the angle of the rifling is always changing, 3) the bullet is supposed to grip the rifling better do to the changing angle of the rifling. Its normally done on a cut rifling lathe with sine bar and instead of the straight bar for the follower a bar with the appropriate radious for the "Gain" is used. There are only a few barrel makers doing this now.

[CLAYPOOL]

Someone needs to mechion Harry Popes work. He was a big Gain Twist promoter , I think.

[Bullshop Junior]

I understand the concept of both the R5 rifling (T/C was using it, and S&W adopted it when they bought out T/C from what I under stand), and the gain rifling.

What I was wondering has anyone here actually used it, and was it better/worse no differance, stripped cast bullets and made them tumble. Just wondering that kind of stuff.

[Artful]

Yes Ol' Harry Pope was a proponent of gain twist rifling.
http://riflemansjournal.blogspot.com/2010/08/history-pope-rifle-barrels.html

http://riflemansjournal.blogspot.com/2011/04/history-directions-for-handling-pope.html

http://riflemansjournal.blogspot.com/2009/08/history-harry-pope.html

http://riflemansjournal.blogspot.com/2010/08/secret-of-old-master.html





What I was wondering has anyone here actually used it, and was it better/worse no differance, stripped cast bullets and made them tumble. Just wondering that kind of stuff.

Look at benchrest most are using cut rifled gain twist barrels to set them world records and it was developed when there was no jacketed bullets. So should have no problems with cast.
http://bulletin.accurateshooter.com/2008/10/gain-twist-cut-rifled-barrels-shine-in-short-range-benchrest/

http://bulletin.accurateshooter.com/2014/08/radical-gain-twist-barrel-for-ar-and-high-power-rifles/

The advantages listed for gain/progressive twist back then where these...

1.) The twist being less at the breech gives less friction to the bullet, it therefore starts easier and quicker, giving the powder less time to burn on in front of the chamber, which therefore fouls less than in a barrel of uniform twist at the same necessary muzzle twist/pitch.

2.) The slight change in angle of rifling in connection with choke boring effectually shuts off any escape of gas and prevents gas cutting, which is another cause of imperfect delivery.

3.) It holds a muzzle loaded bullet in position much better than a uniform/straight twist barrel. ...


https://www.youtube.com/watch?v=qazMwLjR89M

And BS Jr - Wasn't it you that said you didn't like the AR's?

[Tackleberry41]

Doubt the S&W comes with a gain twist barrel. Any I have seen are more money than standard. I think at one point the military did look at gain twist in the shorter barreled rifles. But didnt go anywhere. May have been advantage to it, but cost outweighed those benefits, or just the fact they really hate to change anything.

There are those who really like it, I looked into one a while back for a project, did some research. Consensus seemed to be if it was a game changer, the bench rest people would be all over it. Only place I have really seen it used much was muzzle loaders. Idea was you could run RB down them just as good as sabots, no stripped rifling in fast twist.

[Bullshop Junior]

I'm not a huge fan of AR rifles. But the LGS screwed up on a gun I was trying to buy (finnish nagant that was priced like a russian) and wouldn't give me a refund. So it was either take a loss, or put something else on layaway. Was seriously not ready to shell out $530 (they gave it to me at cost) but the ar was the only thing I really had a use for, and the smith was the cheapest. So I put it on a four month layaway.

[MT Chambers]

Canadian barrel maker Ron Smith makes gain twist barrels that are highly sought after by cast bullet shuetzen shooters.

[Houndog]

There are a few Benchrest shooters using them and I have tried one. I AM NOT impressed with them, but that's MY OPINION! Tracey Bartelin is making the biggest part of them (Bartelin Barrels) The quality of the barrels is certainly there! Tracey used to work at Kreiger before striking out on his own.

[DLCTEX]

I believe that the 460 S&W is indeed a gain twist .

[Blammer]

so how does the rpm theory hold up with gain twist?

[Southpaw 72]

so how does the rpm theory hold up with gain twist?

:popcorn:

[dragon813gt]

so how does the rpm theory hold up with gain twist?

Noooooooooo........why would anyone mention that topic. Thread is sure to be full of chest pounding a bickering now ;) :popcorn:

[nekshot]

Is length a issue with a barrel already on receiver or can they be shortened at will? Seems to me they would do better in a longer application.

[TXGunNut]

My black gun is a S&W, it's several years old but if it has gain rifling I'm not aware of it. Shoots well enough for what it is but I don't reload, let alone cast for it.

[ukrifleman]

I have a Mod 91 6.5x52 Carcano with gain twist rifling. It starts at 1-19 and finishes at 1-8 at the muzzle.

The Italians developed gain twist for the rifle, primarily to extend barrel life.

ukrifleman.

[johnson1942]

ron smith made me a gain twist 45/70 stainless steel barrel many years ago. it starts at 1/26 and ends at 1/22. it is like a mirror in the bore. it is very accurate. I also have a 1/18 twist douglas barrel in the 45 cal. it also is very accurate. cant say if one is more accurate than the other, they both are accurate.

[MT Chambers]

Another theory is that the initial slow twist reduces pressure at the outset.