.25-21 Stevens
Type	centerfire rifle
Place of origin	United States
Production history
Designed	1897[1]
Specifications
Case type	rimmed straight-case
Bullet diameter	.257 in (6.5 mm)
Neck diameter	.280 in (7.1 mm)
Base diameter	.300 in (7.6 mm)
Rim diameter	.376 in (9.6 mm)
Case length	2.05 in (52 mm)
Overall length	2.30 in (58 mm)
Primer type	boxer, small rifle
Ballistic performance
Bullet mass/type Velocity Energy 86 gr (6 g) (smokeless, factory load) 1,470 ft/s (450 m/s) 415 ft⋅lbf (563 J) 86 gr (6 g) (9 gr (0.58 g) smokeless) 1,610 ft/s (490 m/s) 498 ft⋅lbf (675 J) 86 gr (6 g) (5 gr (0.32 g) smokeless) 1,500 ft/s (460 m/s) 434 ft⋅lbf (588 J)
Source(s): Barnes & Amber 1972

The .25-21 Stevens was an American centerfire rifle cartridge.^[1]

Designed by Capt. W. L. Carpenter, 9th U.S. Infantry, in 1897,^[1] the .25-21 was based on the longer .25-25.^[1] It was Stevens' second straight-cased cartridge (after the .25-25)^[2] and would be used in the single shot Model 44 rifle, as well as the Model 44+1⁄2, which first went on sale in 1903.^[2] In addition, it was available in the Remington-Hepburn target rifle.^[1]

While the .25-25 was popular, the .25-21 offered "practically the same performance and was a little cleaner shooting."^[2] 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).^[1]

In power, the .25-21 was outpaced by the .25-20 Winchester^[3] and .32-20 Winchester,^[4] while today, even modern pistol rounds such as the .38 Super offer superior performance.^[5]