Almost any powder that actually works for the 165-175gr is all burned LONG before the end of the pipe.
Any fire-balls that you see at the muzzle isn't from actively burning powder. It is a combination of "glow" or re-ignition once the bullet leaves the muzzle. IF there was enough oxygen in the powder to get a 100% burn(no more fouling!) the temperature would have long melted the barrel.

I agree with Sierra's data on mine with 175 SMK's. Win 748; personally speaking.