JTD, I never thought of loading special loads into magnum brass, but that would have to help with the buildup that happens in the cylinders because of the short "special" brass. I had a little of that fouling to deal with when cleaning yesterday. As far as the Blackout, I have some subsonic loads as slow as 875 fps that still cycle good with bolt hold open on last shot. Yesterday, I was low 900's up to low 10's. This is a 16" barrel with a pistol length gas system and an adjustable gas block that I just don't have to mess with. I have found that 1680 is dirty and loud, but my fav by far is IMR 4227, it is both cleaner and oh, so quiet!!!