I'm confused. Fast powders burn quick with a peaky pressure spike. Slower powders have a flatter pressure curve, imparting more energy to the bullet while never reaching the pressure peak of a fast powder.
So why would we ever use a fast powder? It seems to me that the best possible powder would be one that finishes burning just as the bullet leaves the muzzle. If the charge is complete before the bullet leaves the muzzle, then there was some wasted time where "work" could have been done. If the charge hasn't finished burning by the time the bullet leaves the muzzle, then you have wasted powder.
It would seem that fast powders should be used in short barreled guns. I never hear that, though. Whenever someone asks a "what's the best load for..." question, I don't see people asking for barrel length.
So why would we ever use a fast powder? It seems to me that the best possible powder would be one that finishes burning just as the bullet leaves the muzzle. If the charge is complete before the bullet leaves the muzzle, then there was some wasted time where "work" could have been done. If the charge hasn't finished burning by the time the bullet leaves the muzzle, then you have wasted powder.
It would seem that fast powders should be used in short barreled guns. I never hear that, though. Whenever someone asks a "what's the best load for..." question, I don't see people asking for barrel length.