.38-40 Winchester

Winchester introduced the .38-40 in 1874, necking its own .44-40 case down to a bullet just over 10 mm in diameter to sit between that round and the smaller .32-20 in the same rimmed, bottlenecked family. Despite the “38” in its name the bullet is actually .40 caliber — a long-standing naming quirk of the black-powder era, when a cartridge’s name described the powder charge and bore loosely rather than a precise bullet diameter. Like its siblings it was built so a Winchester lever rifle and a period revolver could share one box of ammunition.

Colt and other makers chambered revolvers for it specifically to pair with the Winchester 1873 and 1892 rifles, and the round stayed in production until 1937, by which point the dual-caliber rifle-and-revolver arrangement it was built around had fallen out of fashion. It returned to production in 1993, driven by the growth of cowboy action shooting, and modern loadings — including specialist heavy loads for the stronger revolvers and rifles still chambered for it — are again commercially available.

Case, bullet and pressure figures here are transcribed from the current C.I.P. datasheet and are verified. Buffalo Bore’s own product page for its 180-grain hard-cast load states two muzzle velocities, one from a 5.5-inch revolver and one from a 24-inch rifle, both with the barrel length named — which is what lets this entry carry two sourced velocity points for the same bullet weight rather than the single, barrel-length-free figure that most other published sources for this cartridge give.