.22 Spitfire

The .22 Spitfire (also known as 5.7mm Johnson or MMJ 5.7mm Johnson ) is an American  rifle cartridge.

Designed by Melvin M. Johnson of Johnson Guns Inc. for their conversion of the M1 carbine, this wildcat was introduced in 1963. It was based on the .30 carbine, necked-down to .22 (5.7mm).

It is suitable for rabbits, coyotes, or other varmints, and has potential as a military round.