Re: Transitional Rifling?
Gain twist has no real effects on velocity or pressure levels. The main benefit is that by applying a small amount of increase in the twist rate, the bullet will be under constant resistance. It forms a physical choke, for lack of a better description. It appears that this will extend the secondary pressure curve slightly, and keep the barrel stretching forward for a longer period of time. This will dampen harmonic vibrations for a longer period of time and improve accuracy.
We have had the best results with a very small increase in twist rate, usually from .5 to 1.0 inch of increase in the twist rate over the length of a barrel. For example, a .308 Win would start at 12.0 twist and increase to 11.25 at the muzzle.
Some of the benchrest shooters that use our barrels have been experimenting with increases as small as .1 inch of increase with very good results.
Some ELR shooters have been experimenting with much more radical twist rates but as of yet no scientific results have been reported.