The Answer Is In The Powder. You Just Can Not Get Smokless Performance From B.p. The Muzzle Loader Is Going To Shoot W A Y Slower Due To The Powder!!! Now, If You Were Talking About The One Muzzle Loader That Actually Can Shoot Modern Smokeless Powder, Then I Could Not Give You Any Reasons. Mostly, Because I Do Not Know Much About That Particular Firearm. Here In Michigan, You Must Use Bp, Or Bp Subs To Hunt With A M.l., At Least During The M.l. Season. For Me Its A Moot Point. I Own A 45/70, And A 50 Cal M.l. For M.l. Season. 45/70 Performance From A M.l. Just Isnt Going To Happen With Bp Or Subs.