Gain twist rifling questions

Can a rifle with gain twist rifling be accurate with cast boolits? I am only aware of the Carcano using this method. It would seem the rifling would be continuously distorting the boolit surface as it passed thru the barrel. I assume the Italians chose the gain twist rifling to accommodate the high sectional density bullets they went with, but other countries designs seemed to do fine with equally long bullets and conventional rifling. Anyone here successfully used cast boolits in a gain twist barreled rifle?

Some of the old black powder revolvers used gain twist rifling. If it worked for soft round ball, it should work for boolits.
I have no experience with gain twist rifles.

Harry Pope's barrels were rifled with a gain twist and seemed to work fairly well. There wasn't much of a change though. S&W 500 revolvers are also gain twist with a fairly big change and they shoot cast well. But it does seem like it would cause leaks on the back side.

Colt used gain twist in the Patterson and later, I'm not sure when he went to a standard twist. Worked for him. I think the idea is that the boolit gets an easier start with less distortion with the slow initial twist.

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Originally Posted by Nobade

Harry Pope's barrels were rifled with a gain twist and seemed to work fairly well. There wasn't much of a change though. S&W 500 revolvers are also gain twist with a fairly big change and they shoot cast well. But it does seem like it would cause leaks on the back side.

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"work fairly well" perhaps a understatement.

Quote:

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Originally Posted by Nobade

Harry Pope's barrels were rifled with a gain twist and seemed to work fairly well. There wasn't much of a change though. S&W 500 revolvers are also gain twist with a fairly big change and they shoot cast well. But it does seem like it would cause leaks on the back side.

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I recall reading an account by Pope, and he said although he and other shooters had made gain twist barrels, they never did really establish that one was better than a straight cut barrel.

Interesting discussion at

http://www.shilohrifle.com/forums/viewtopic.php?t=7632

Another here at

https://www.snipershide.com/shooting...-twist.201720/

It looks like the use of gain twist rifling was/is a much less commonly used method of stabilizing a small arms bullet than I realized. Did any of the major powers go this route ( besides Italy) with their rifles/carbines? The places I looked didn’t give much information. Any info regarding use of cast boolits in a rifle using a gain twist would be greatly appreciated. And thanks for the references posted!

I have a 6.5 x 57 with a gain twist barrel
It is a Brno CZ

I never really tried a lot of cast bullet loads in it
But if I use a bullet cast from Lino , it shoots great
The 2 that I found that worked well were
The 140 gr RCBS Silhouette Rifle Bullet mold
The NOE 266-140-FN-BY2 2 Cavity GC mold

I was able to borrow the molds to try
If I was going to shoot more cast out of the rifle I would get the NOE mold

John

Gain twist rifling is frequently used in larger caliber weapons. In 20mm M61 barrels one can plainly see the rifling starts out very slowly and increases to a faster spin over its length. 20mm is a fairly hot load but I can tell you from first hand experience when the barrels are removed from service it isn’t uncommon to see portions of the lands literally ripped out of the barrel.