Powder type and amount does make a difference. And as most rifles with all sorts of barrel lengths show flames coming out of the muzzle if observed in total darkness, that's usually considered proof that there's still powder burning outside the barrel. And with some loads of some powders, unburnt granules can be seen on the ground in front of the muzzle
+1
By choosing a faster powder than the ones at the top of the list for my 16" barrelled Ruger Frontier, I get a whole lot less flash and blast out of the muzzle, less recoil, and don't lose nearly as much velocity as one would think out a barrel 8" shorter than what the load data was developed in ....