Ok you ballistic sages, edgamicate me. Is there any relation between powder burn rates and the length of the barrel? It is obvious that slower burning powders are for longer barrels. This is evident by the difference between pistol and rifle powders. But when you get to many of the rifle powders, barrel length seems to have little influence on the use of specific burn rates. Is it the weight of the bullet and its resistance to initial movement? If you have a .450 Marlin in 24inch barrel and .300 Win Mag in the same length, why the difference in powder burn rate? If so, it would seem to me that you would want to build pressure behind the heavier bullet slower than the lighter bullet, yet this is not the case.