Winchester introduced the .22 Winchester Magnum Rimfire (WMR) in the 1950's. It was the first new .22 rimfire cartridge in decades. Its long case contains a lot more powder than the Long Rifle, and the cartridge operates just about at the pressure limit for rimfire ammunition. Like the Long Rifle, the Magnum is chambered in a variety of rifles and revolvers. For the handgunner, one of the neatest of these is the single action "convertible" revolver that is supplied with two interchangable cylinders, one for .22 LR cartridges and one for .22 Mag. cartridges.

Bullet diameter for the Magnum is .224", the same as for the .22 WRF and most centerfire .22's. Its case is slightly fatter than a Long Rifle case and, as loaded by Winchester-Western, the Magnum's original 40 grain bullet came with a real jacket, not just copper plating. Bullet styles include full metal jacket (non-expanding) and jacketed hollow-point (expanding) types. The SD of the 40 grain bullets is .114. As originally loaded a MV of 2000 fps was claimed from a 22" rifle barrel, and 1550 fps from a 6.5" handgun barrel.

Available bullet weights have expanded to include 30 grain and 50 grain bullets (SD .142) in addition to the original 40 grain bullets. CCI, Federal, Remington, and Winchester all load .22 WMR ammunition. There is also a .22 WMR shot cartridge, loaded with #11 shot.

The standard 40 grain bullet is now advertised to have a muzzle velocity of 1,910 fps in a 22" rifle barrel and carries 324 ft. lbs. of energy. From the 6.5" barrel of a revolver the velocity is 1400 fps with an energy of 174 ft. lbs.

The .22 Magnum is a much more powerful cartridge than the .22 LR. At 100 yards its 40 grain bullet is still carrying 156 ft. lbs. of energy, more than the .22 LR develops at the muzzle (compared in 22" barrels). The flat shooting WMR can be zeroed to hit +0.6" at 100 yards when fired from a scoped rifle, and will give a point-blank range (+/- 1.5") of about 124 yards.

The power of the Magnum, coupled with the violent expansion provided by its JHP bullet, makes it too much cartridge for shooting cottontail rabbits and squirrels at close range unless only head shot are taken. Body shots tend to literally blow these small animals apart.

Used for self defence in a revolver, the .22 WMR has compiled a 42% one shot stop rate according to Marshall and Sanow. This is far superior to the .22 LR and .25 ACP, and makes the .22 WMR the best of the small bore handgun cartridges.

Within its trajectory limitation of about 125 yards, the extra destructive power of the .22 Magnum's JHP bullet moves it into the varmint rifle cartridge class. Its low report makes it one of the best varmint cartridges for shooting on the small ranches and farms typical of semi-populated areas and in the country outside of small to medium sized towns.

For years there were lever, pump, and bolt action rifles chambered for the .22 Magnum, but very few autoloaders. This is because the Magnum operates at pressures above those deemed safe for simple blowback actions (the type of action used for all autoloading .22 LR rifles). The rifle manufacturers seemed to have licked the problem in recent years, however, as there is now a selection of autoloading sporting rifles chambered for the .22 WMR. For the serious small game and varmint hunter there are a number of accurate, high grade .22 Magnum bolt action rifles.