pistol/rifle twists

PRB pistol twist is usually fast, real fast.

Rifle twist usually slows waaaay down for PRB.

Why is bullet shape not the detirmining factor here?

What length is the crossover point?

Will a .50 rifle with a 15" barrel need 1:60 while a .50 pistol with a 14" barrel need 1:10.

Should we be adjusting the twist to the barrel length suitable for the gun rather than the projectile we intend to shoot?

:front:

 

[B.Habermehl]

Muzzle velosity is the key the slower the mv. the faster the twist has to be for stability. Just as a 1 in 48 twist rifle barrel will usually have a milder optimum load than a 1 in 72 twist barrel of the same caliber and manufacturer. Your pistol ball will be travelling around 600 to 900 fps verses a rifle ball traveling at around 1400 fps. Even if the twists are the same there will be a big diference in rotational speed (RPM) of the ball due to the velosity difference. Thats why the pistol barrel has a faster twist than the rifle barrel. It is all about getting the ball up to the optimum RPM for stability with out over spinning the ball and amplifing its imperfections. BJH