
The iconic Tommy gun fires .45 caliber handgun ammunition. That makes it a submachine gun. (Shutterstock photo)
TLDR: Submachine guns use handgun ammunition. Machine guns use rifle ammunition.
If a gun-toting character pulls the trigger and holds it there while the business end goes bang-bang-bang, then there’s an excellent chance that firearm is a submachine gun or a machine gun (warning: does not apply to characters requesting someone pull their fingers). But what’s the difference between those two terms? Or is there one?