.41 Short

The .41 Rimfire Cartridge was first introduced by the National Arms Company in 1863 and was also known as the .41 Short and the .41-100. In most designations like this, the second number refers to the black powder load, though in this case it means "41 hundredths of an inch". According to "Cartridges of the World," the .41 Rimfire consisted of a 130 grain (8.4 g) lead bullet propelled by 13 grains (0.8 g) of black powder in its original load. The round produced a muzzle velocity of 425 ft/s and a muzzle energy of 52 ft.lbf. In contrast, modern low-powered smokeless cartridges produce considerably more energy: .380 ACP (200 ft·lbf), .22 LR (100 ft·lbf).

Performance
Cartridges of the World states that when fired at a hard object, such as a tree, from a distance of 15 yd or more, the bullet often bounces off. Reportedly, when shot at a target more than 20 yards away, the shooter hears two distinct reports; First the gun being fired; and second, the lead bullet striking the target. The .41 Short was created with the intention that it be used in a small, single-shot derringer, which likely is the reason for the very low ballistics (most derringers were and are chambered for cartridges that were not originally intended to be used in such a small weapon). Remington Arms began producing their famous Remington Model 95 over/under double barrel derringer chambered for the .41 Rimfire cartridge in 1866.

Uses
A National Arms .41 Rimfire derringer was recovered from the battlefield of the Battle of Little Bighorn. Estate records reveal that it belonged to Brevet Major General George Armstrong Custer, the commander of the soldiers slain in the battle.