A cowboy-era dual-use cartridge chambered in both Winchester rifles and Colt revolvers. Despite the name, it fires .40-caliber bullets — a frequent source of confusion.
Type: Pistol
Introduced: 1874, United States
Parent case: .44-40 Winchester
Standardization: SAAMI
Bullet diameter: 0.401" (10.19 mm)
Case length: 1.305" (33.15 mm)
Overall length: 1.592" (40.44 mm)
Max pressure: 14,000 PSI
Rim type: Rimmed
Primer: Large Pistol
Typical twist rate: 1:36
Muzzle velocity: 1050–1320 fps
Muzzle energy: 440–695 ft-lbs
Effective range: 100 yd
Common bullet weights: 180 gr
Primary use: Cowboy Action, Self-Defense
Production status: Active
Also known as: .38 WCF · .38-40 WCF · 38-40
History: The second in Winchester's rifle-revolver cartridge series (after .44-40). The '38' in the name refers to the case mouth diameter, not bullet size — it fires .401" bullets. Became the preferred cartridge of many lawmen and outlaws who wanted one ammunition type for both rifle and revolver.
Notable firearms: Winchester Model 1873, Winchester Model 1892, Colt Single Action Army, Colt Lightning
Similar cartridges: .44-40 Winchester, .32-20 Winchester, .45 Colt