I'm with Indian Joe here. BP develops full velocity and pressure by exploiting adiabatic expansion from longer barrels. Only Swiss BP is as good as old Army A5 which was used for .45-70 Trapdoor, Schofield and Navy line throwing loads into the Vietnam era. When I was an enlisted rating we still had converted Springfield trapdoors used as line throwers, with 26-inch barrels, which began to be replaced by H&Rs in the Zumwalt era. I used to pull a few of the wads, expand the case mouth, seat Remington 405-grain softpoints over the BP charge with a blob of lithium grease and had the ship's machinist braze an M1 front sight and open rear from an M1911 pistol on them, cutting down the blade to zero and they were good enough to pop mines at 200 yards off the fantail. Great fun!