.22 ILARCO

The .22 ILARCO / 5.7x24mmRF, also known as the .22 Winchester Short Magnum Rimfire or .22 American, was a rimfire cartridge designed in 1987 for the American-180 rimfire submachine gun. At the time the cartridge was created, the design of the American-180 had been taken over by the Illinois Arms Company, Inc., hence the ILARCO name.

History
Sometime after the Illinois Arms Company, Inc. (ILARCO) purchased the rights to the American-180 they determined a more powerful cartridge would be appropriate, which resulted in the creation of the .22 ILARCO. The new cartridge was designed so that a simple change of barrel was all that was required to switch between standard .22 Long Rifle, for which the gun was designed, and the new cartridge.

Dimensions and loading
The .22 ILARCO uses a shorter version of the .22 Winchester Magnum Rimfire case, which use the same 40 gr projectile as the original .22 Winchester Magnum Rimfire cartridge.