i have a 460 S+W mag 8 3/8" barrel (and recently purchased a 18" Raptor barrel, yet to be fired. I'm waiting on a gas block.). The muzzle blast/flash of the 460 with max load of AA#9 is considerably less than H110/Win 296. Empirically, this leads me to think there is a lot of still burning H110/Win296 behind the bullet when it exits the muzzle. Powders slower than IMR 4227 may not be needed in a straight wall case using relatively light for caliber bullets in a rifle with a mid length gas system. Bullets over 300 grains may be a different story.