If I remember right it started out as a wildcat from the 20's. It is a necked up .30-06 case. You still see it chambered for rifle's and lever actions now and again but it is still most popular in the contender/encore platform. One of the bigger draws to the cartridge is the bullit selection anything from light .38/.357 pistol to around 300 grain thumpers. Varmint to big game in one cartridge.