Im sure this is common knowledge, but I have not seen anything about it. I built a little 556 pistol with a 10.5 inch barrel, and have heard that pistols do not burn all the powder. Is it common to use a faster burning powder for smaller barrels in order to get adequate velocities? Does it really matter, i mean how much unburnt powder are we talking about? Ultimately this is going to be a fun (loud) plinker that will probably stay in the truck when in the woods, but mostly i had an itch to build something new.