The .22 Remington Automatic (also known as the .22 Remington Auto and occasionally .22 Rem Auto) is a .22in (5.6mm) American rimfire rifle cartridge. Introduced for the Remington semiautomatic rifle in 1916, the .22 Rem Auto was never used in any other firearm. It will not chamber correctly in other .22 rimfire weapons, nor will other .22 rimfire ammunition, including the dimensionally very similar .22 Winchester Automatic, interchange with it. This feature was to prevent use of black powder rounds, which were still popular when it first appeared, from being used in the Model 16, resulting in powder residue rapidly clogging the action and rendering the weapon inoperable.