The .225 Winchester / 5.7x49mm cartridge was introduced in 1964 by the Winchester Repeating Arms Company.
The .225 Winchester cartridge was derived from the .219 Zipper case, though its rim diameter was reduced to accommodate the standard .473-inch bolt face. It was developed with the goal of supplanting the .220 Swift, a cartridge that had earned a reputation for accelerated barrel erosion. Although the .225 Winchester featured a more modern, straight-tapered case design, it was ultimately overshadowed in popularity by the older .22-250 Remington, which had already gained widespread acceptance as a wildcat cartridge before being commercially standardized one year later.
Factory rifles chambered for the .225 Winchester were produced by WinchesterâÂÂnotably the Model 70 and Model 670âÂÂas well as by Savage Arms in the Model 340. All mass-produced firearms offered in this chambering were either bolt-action or break-action designs. Winchester discontinued rifle production in .225 Winchester in 1971; however, the company has continued limited seasonal manufacturing of factory ammunition and cartridge cases. Reloading dies remain commonly available, and cartridge brass can also be formed from .30-30 Winchester cases with appropriate modification.
The .225 Winchester's case is a parent case for some of SSK Industries' popular line of JDJ cartridges designed by J.D. Jones, chosen for its strength and semi-rimmed design which makes it well suited for use in break-open actions.