Winchester developed this underestimated round in 1959. The concept of the .22 Magnum or .22 WMR—the two terms are interchangeable—comes from Winchester’s .22 WRF round first introduced in 1890. Though the .22 Magnum is a .22 caliber, it is longer and thicker than a .22 Long Rifle round. It also holds more powder and can handle higher pressures. Therefore, the two are not interchangeable. Traditionally, the .22 WMR utilizes a 40-grain jacketed hollow point bullet, but .22 WMR ammunition varies today in that you have your pick from a wide variety of varmint, hunting, and plinking rounds.
.22 WMR is a rimfire cartridge, which means the primer is in the rim of the cartridge. The firing pin hits the rim of the cartridge to ignite the bullet.
The .22 Magnum is an effective small game and varmint round. Knock-down power for varmints is good up to 125 yards and 50 yards for small game. With the right bullet, distance, and shot placement, a .22 Magnum can even take down a coyote. Because the .22 Magnum can hold more power, velocities reach up to 2,000 feet per second from a rifle and 1,550 from a handgun.
Though Winchester developed the round, it was Ruger and Smith & Wesson that first had guns to shoot it. Both initial guns were revolvers, and later Savage made a rifle for the .22 WMR called the Model 24. Winchester also produced the Model 61. In 1977, H&R made the first semi-automatic rifle chambered for the .22 Magnum. There was even a machine gun chambered for it, the EDDA. Today there is a large choice for .22 Magnum revolvers and bolt-action rifles, but very few semi-automatic rifles and handguns. The latest to enter the market is the semi-automatic Kel-Tec PMR-30 handgun.
As far as performance goes, the .22 Magnum is good for prairie dogs, ground hogs, squirrels, snakes, rabbit, turkey, and other small varmints. If you are going to hunt edible game with a .22 Magnum, shot placement is of the utmost importance. As the most powerful rimfire cartridge available, it has the ability to blow away small game and destroy the meat. This is especially true when hunting rabbit or squirrel. Without getting into a discussion about the knock-down power of self-defense rounds, Marshall and Sanow give the .22 WMR a 42% rating in one shot to stop a two-legged threat. This is a better rating than the .22 LR and the .25 ACP. For self-defense, experts recommend a jacketed hollow point bullet, because the hollow cavity in the bullet allows for expansion when it hits mass. Hornady’s self-defense round, the Critical Defense 45-grain FTX bullet is comparable to the .380 ACP in terminal ballistics. North American Arms produces quite a few choices of their Mini Revolvers and the Pug in .22 Magnum. The NAA revolvers are highly concealable, a true pocket gun perfect for back up self-defense.
When I was researching this surprisingly powerful load, I found that many people have no confidence in its accuracy, however the .22 Magnum is excellent in maintaining its trajectory and produces less than 1-inch groups at decent distances.
I tested Armscor 40-grain jacketed hollow point rounds in a 1960 S&W Model 51 revolver with a 3-1/2-inch barrel. Armscor makes their ammunition in the United States and each round is polished and consistent. The ammo boosts the muzzle velocity to about 1875 feet per second. I like Armscor because if you find one faulty round in your box, they will replace the whole box free. Armscor is also one of the most affordable brands that Cheaper Than Dirt carries. In price, it competes with Fiocchi. This makes sense because Armscor makes ammunition for Fiocchi. That is why you will find the F headstamp on Armscor .22 Magnum ammunition.
Even though I did have one failure to fire in the first rotation through my cylinder, I put it through again and had no problems. The long trigger pull on my S&W takes a few rounds to get used to, but once you have a feel for it, shots are accurate with no flyers. The recoil on the .22 WMR is minimal, which means you get better groups. I read that .22 Magnum performs better in revolvers than in rifles, but I have not had a chance to test the theory.
The .22 Magnum does fall short at long ranges, as does any rimfire cartridge. For optimum performance, shoot the .22 Magnum at no further than 125 yards. Due to their size, any .22 caliber round can handle only so much pressure before the load becomes dangerous. Regardless, the .22 Magnum is more powerful than any other rimfire caliber.
For versatility, price, and accurate performance, the .22 WMR is one of my favorite rounds.