[id10t]

So my buddies that play in teh land of smokeless powder muzzle loaders do a lot with this. Cartridge guns going .001 over groove diameter is fine, as is full engagement, or in my case partial engagement with a flat base bullet and a powder with enough kick to make it fully obturate. With a front stuffer of any type though, you gotta get that bullet down the bore first.... If not using sabots (which does make things easier...and a 195-225gr .40 cal bullet at 2600fps is nothing to sneeze at) they always use flat base bullets (boat tails won't properly obturate and engage rifling) and they size them to run down the bore with only .001 or .002 of engagement in the rifling. The other choice they go with is to use a piece of their barrel cut off when having their guns built and making a full-engagement sizing die, so they pre-engrave the bullet with the barrels rifling so it is easy to load and already has near full engagement. And to make all of this work with proper obturation, they use a few select powders that are fast enough to give a quick kick in the pressure but slow enough to be a rifle powder for a 24"+ barrel (N110, N120, and other stick powders). And to be honest, they do some absolutely amazing stuff that is competing with centerfires - and winning. Well under MOA groups at 500+ yards...