Changeling, the only use I have heard of for gain twist barrels is shooting round balls in blackpowder guns. You would have to have a short bearing surface or the differing rate of twist would cause the rear of the bullet to strip off material because it would be spinning slower than the fron of the bullet. Page 209 of Elmer Keith's "Sixguns" gives a description of the use of this type of rifling.
Hitman, what you say could very well be correct if a person was talking about "extremely fast" twist changes. However, the changes I am contemplating are not to be considered "fast". I also realize and am well aware that every so often someone comes along extolling the virtues of gain twist rifling.
I have spent considerable time, effort, and expertise into an idea that I have about "Gain Twist" barrels and there use. The only problem I am now having is finding a company that can perform "Gain Twist" in 45 caliber! A search of the internet has not come up with a company that is tooled to work at that caliber.
I appreciate your consern, but I am sure I know what I am doing. If not, "nothing ventured, nothing gained".
If you are spinning the front of the bullet faster than the rear, the actual "rate of twist" is inconsequential. It's all about relative rates of twist. I do not know what your definition of "fast" is, but on a gain twist barrel, you start at zero and get progressively faster as you go.
Why don't you consullt with some barrel makers and see if they will build a gain twist barrel for you? That seems like the logical thing to do. I'm sure most of them have some expertise in this area also.
Precision Shooting Magazine http://www.precisionshooting.com/ had an article "What About Gain Twist Barrels?" by M.L. McPherson in the April 1999 issue. He spends most of the article speculating on the effects of gain twist on the bullet and the barrel. Mic gets a bit convoluted here, no surprize if you're familiar with his writing style. He ends with a report on a .308 light varmint gain twist barreled rifle of Pete Forras' that's shooting Barnes X-bullets into 1/2 MOA groups. The barrel was made by Ron Smith, RKS Enterprise Ltd., 403-631-2405 (Alberta, area code might be 780 now).
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