Thought about this last night if you shoot muzzle loaders and do not seat the projectile on the powder it is considered a "short start" and is dangerous and may blow up your barrel. So why can you get by with space between the powder and the bullet in a cartridge????????? Gonna load up some cast using powders like 2400 and unique and I know I will have air space. I know it is safe or the loads would not be published. Just wondering why in a cartridge you can get by with it?

Because black powder is an explosive and smokeless powder is a flammable

Yea I know that, but there has to be more to it than that.

No, I think Steve has it right. Black powder goes bang like right now, immediately if not sooner, whiles smokeless powder deflagrates, that is it builds up pressure slowly as it burns, thus allowing the bullet to start moving before the pressure gets high enough to be damaging. Of course, this all takes place in milliseconds and it would seem that both are "exploding" at the same rate, but in reality, they are not.
In Hunter Ed class, we demonstrate this by laying a trail of smokelss powder in a piece of angle iron leading up to a small amount of black powder. it takes about two seconds for the burning smokless to reach the black powder which then goes up in a spectacular "WHOOSH" and big cloud of white smoke. Impresses the hell out of the kids and even most of the adults every time.
Paul B.

OK Thanks for the info now I know.