By the way, for the record:
Bullet: Durr.
Clip: A set of bullets. Some guns (1800 – 1950) have a box on the gun where you put clips directly. Modern times, you put clips as a set into…
Magazine: A plastic container that holds bullets. You can put bullets in the magazines individually or put them in as clips. You probably want to hold on to these.
Round: A round is basically how many bullets a gun can hold at once.
Pistols magazines, as far as I know, can’t can’t accept clips and have to have individual bullets inserted into them. Rifles can take clips, but we don’t have any. For the pistol, I suggest saying “$xx per round”, but since that mistakenly used so often (even in the military), “$xx per magazine” might be more suited. Of course, the former does not actually include the plastic magazine.
Also, one final thing: Shotguns don’t use bullets, they use shells.