Home Forums Hunting & Shooting Muzzleloaders questions on upcoming elk hunt

Have tag for an upcoming black powder elk hunt here in Idaho. A whole new thing for me, have never shot any game with BP. Have a choice of two rifles to use, a 50 cal. Cabelas 20" carbine, or another Italian made rifle with a 28" barrel. Is there much velocity loss with the shorter barrel ?
Also will be using either Thompson mini ball ,350 grain, or also have some Buffalo bullet 385's. and either FFG, or pyrodex. And where do I find load data ?
Thanks.