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.