.22 Magnum

.22 Winchester Magnum Rimfire
.22 Winchester Magnum Rimfire
Type	Rimfire
Place of origin	United States
Production history
Designed	1959
Manufacturer	Winchester
Produced	1960–present
Specifications
Parent case	.22 WRF
Bullet diameter	.224 in (5.7 mm)
Neck diameter	.242 in (6.1 mm)
Base diameter	.242 in (6.1 mm)
Rim diameter	.294 in (7.5 mm)
Rim thickness	.050 in (1.3 mm)
Case length	1.055 in (26.8 mm)
Overall length	1.350 in (34.3 mm)
Rifling twist	1-16"
Primer type	Rimfire
Ballistic performance
Bullet mass/type Velocity Energy 30 gr. (1.9 g) HP 2,300 ft/s (700 m/s) 322 ft·lbf (437 J) 40 gr. (2.6 g) JHP 1,875 ft/s (572 m/s) 324 ft·lbf (439 J) 50 gr. (3.2 g) JHP 1,530 ft/s (470 m/s) 300 ft·lbf (410 J)
Test barrel length: 24 inches (610 mm) Source(s): Cartridges of the World

The .22 Winchester Magnum Rimfire (5.6×27mmR), more commonly called .22 WMR, .22 Magnum, or simply .22 Mag, is a rimfire cartridge. Originally loaded with a bullet weight of 40 grains (2.6 g) delivering velocities in the 2,000 feet per second (610 m/s) range from a rifle barrel, .22 WMR has also been loaded with bullet weights of 50 grains (3.2 g) at 1,750 feet per second (530 m/s) and 30 grains (1.9 g) at 2,250 feet per second (690 m/s). More recently, a high-quality 30gr Vmax cartridge from Hornady has been released. This exceeds 2200fps in a rifle and has a reputation for much greater consistency and accuracy than was previously attributed to this calibre. Accuracy around 1 MOA is achievable and this has led to this cartridge regaining ground previously lost to the excellent .17 HMR, especially as the 30gr bullet weight (nearly double that of the HMR's normal 17gr) gives it a reputation for hitting harder on larger varmints such as fox and coyote.

The .22 WMR was introduced in 1959 by Winchester, but was not used by Winchester until the Winchester Model 61 slide rifle could be chambered for it in 1960. By that time, Smith & Wesson and Ruger had revolvers for it, and Savage had come out with the Model 24 and since late 2012, the model 42, a more modern update than the 24, a .22/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. The combination of more powder and higher sustained 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 per second (460 m/s) from a handgun. A .22 WMR round will not fit into the chamber of a .22 LR firearm, but it is possible, though unsafe, to chamber .22 LR rounds in a .22 WMR firearm, although doing so can result in injury from gas leaking around the LR case which is undersized for a magnum chamber.