.280 in (7.1 mm)
Place of origin
.257 in (6.5 mm)
.300 in (7.6 mm)
The .25-21 Stevens was an American centerfire rifle cartridge.
Designed by Capt. W. L. Carpenter, 9th U.S. Infantry, in 1897, the .25-21 was a bottlenecked round, based on the longer .25-25. It was Stevens' second straight-cased cartridge (after the .25-25) and would be used in the single shot Model 44 rifle, as well as the Model 44½, which first went on sale in 1903. In addition, it was available in the Remington-Hepburn target rifle.
While the .25-25 was popular, the .25-21 offered "practically the same performance and was a little cleaner shooting." It was also found the usual 20 or 21 gr (1.30 or 1.36 g) black powder charge of the shorter, bottlenecked .25-21 offered "practically the same ballistics" as 24 or 25 gr (1.56 or 1.62 g) in the .25-25. It was highly accurate, reputedly capable of generating .5 in (12.7 mm) groups at 100 yd (91 m).
In power, the .25-21 was outpaced by the .25-20 WCF and .32-20 Winchester, while today, even modern pistol rounds such as the .38 Super offer superior performance.