The .22 WMR uses a larger case than the more popular .22 Long Rifle, both in diameter and length. The .22 WMR's case is thicker, allowing higher pressures. The combination of more powder and higher pressures gives velocities over from a rifle using a bullet, and per second (460 m/s) from a handgun.
If sighted in for maximum point blank range on a high target, the .22 WMR can reach ranges of nearly 125 yards. This makes the .22 WMR an effective short to medium range varmint rifle cartridge. The relatively quiet sound of firing and negligible recoil also make it a very pleasant round to shoot for extensive periods of time. It is less expensive to shoot than its nearest competitors, the centerfire .22 Hornet, the .17 HMR, and the new 5.7 x 28 mm.
The .22WMR is little more than an enlarged, more powerful version of the much earlier .22 WRF (which can also be fired in any weapon chambered for .22WMR). It was for a time the most powerful rimfire round available, and even outperformed the .22 WCF.
While more powerful than the .22 Long Rifle, ammunition is not available in as large a variety as .22 LR. Availability is also not as great, either; while the .22 WMR is by no means hard to find, nearly every retailer that sells ammunition will carry .22 LR. The price of .22 WMR is substantially higher than almost all .22 LR, though it is less expensive than the new .17 Rimfire calibers. Since many of the rifles that chamber the .22 WMR use tubular magazines, bullet noses are generally flat or blunt to allow smooth feeding. Recently, new bullets have emerged from Remington, CCI, and Hornady and have 30 or poly-tipped ballistic tips.While a pointed bullet is not going to rest against the primer of the round in front of it (like in a centerfire cartridge), a pointed bullet could still hang on the manufacturer's stamp, which is found in the middle of the base of the cartridge.
Due to the limited selection of commercial ammunition, the .22 WMR was the case used by a small but dedicated group of wildcatters for handloading high performance rimfire ammunition. Generally these loads would use more aerodynamic pointed bullets, the same type used by .22 caliber centerfire cartridges. While often heavier than standard .22 WMR bullets, the sharp nose and tapered tail retained velocity better, and delivered more energy downrange. Other wildcatters would neck the .22 WMR down to smaller calibers, such as .20 (5 mm) and .17 (4.5 mm) or even smaller, in an attempt to get maximum velocity and the flattest possible trajectory.
The .22 WMR is effective out to 125 yd (115 m) and capable of handling varmints such as coyotes or wolves, but too destructive for small game, such as rabbits or prairie dogs or anything intended for eating.