The term "submachine gun" was coined by John T. Thompson, the inventor of the Thompson submachine gun, to describe its design concept as an automatic firearm with notably less firepower than a machine gun (hence the prefix "sub-"). ... After the war, new SMG designs appeared frequently.

What makes a machine gun a submachine gun?

The Difference: Caliber and (sort of) Size

That can be true, but it's a little backward. Submachine guns use handgun ammunition, and are basically dressed up pistols. Machine guns use rifle ammunition, and are basically dressed up rifles.

What the difference between a submachine gun and an assault rifle?

SMG weapons generally have low recoil and offer a straightforward recoil pattern to the user. On the other hand, the Assault rifles come with high recoil and this also affects the aim of a player. ... Thus, beginners are advised to use SMG weapons to improve their gun handling skills.