Just what I was going to say. There's a column of air ahead of the bullet, and it's moving just as fast and forceful as the round itself. It'll clear out anything well ahead of the bullet.Buy watching a slow motion/high speed video of cartridges being fired ... You will see a column of air and hot gas exist the barrel before the bullet exists the barrels ...
I believe that to be a "piston type air compressor" ... most likely at high velocity also ...