This Type of gun was produced for World War I & peaked during World War II, in moden times submachine guns or smg have been mostly superseded by assault rifles which have a greater power for penetrating body armour that's used by modern soldiers. but they still have their place in any battle especially Airsoft "CQB" or Close Quarters Battle. The term "submachine gun" was first used by John Thompson, the creator of the Thompson Tommy gun. Some of the most popular bb gun models of smg are sten gun, mp40, uzi, p90, mp5, and mp7 also some of the ak47s with a folding stock are also classed as a smg. We have smg replicas that are gas powered, but more commonly spring and electric aeg's in the norm.