The .22 WMR was introduced in 1959 by Winchester
, but was not used by Winchester until the venerable Model 61 slide
rifle could be chambered for it, well into 1960.
By that time, Smith and Wesson
for it, and Savage
had come out with the Model 24
, a .22/.410 combination rifle
. It was the only successful rimfire cartridge introduced in the 20th Century.
The .22 WMR uses a larger case than the more popular .22 Long Rifle
, both in diameter and length. The .22 WMR case is a lengthened version of the older .22 WRF
(.22 WRF may be fired in a .22 WMR but not vice versa). The .22 WMR's case is thicker than that of the .22 LR, allowing higher pressures. The combination of more powder and higher pressures gives velocities over 2,000 feet per second (610 m/s) from a rifle using a 30-grain (1.9 g) bullet, and 1,500 feet (460 m) per second (460 m/s) from a handgun
. A .22 WMR round will not fit into the chamber of a .22 LR firearm but is possible to chamber and fire .22 LR rounds in a .22 WMR firearm. This is potentially hazardous due to the difference in case diameter. When fired, the .22 LR case expands in the chamber, which can cause the case to split open or become stuck. Also, the long rifle bullet will travel in the magnum chamber unsupported for .4" before entering the barrel causing leading in the chamber. .22 Magnum Rim Fire and .22 Winchester Magnum Rimfire are two names for the same cartridge.
Some companies just don't like to use another company's name on their product.