Hand Cannon

From the American Rifleman. Taurus introduces the Model 405, a 2 inch snub nose revolver. The quintessential American hideout gun, Small, dependable, and powerful. Usually chambered for .38 Special.
Only this snubbie is chambered for .40 Smith and Wesson, an automatic pistol cartridge. Revolver cartridges have a rim that seats on the cylinder and holds the cartridge in place against the blow of the hammer, and gives the extractor something to grab onto. Automatic pistol cartridges are rimless, to make them seat nicely in the magazine and feed smoothly. The maker sells the gun with half moon clips, a steel disk with cutouts to grab onto the .40 S&W rounds extractor groove. One half moon clip accepts 5 rounds, ready to drop into the cylinder.
The .40 S&W round is hot, the 405 achieves 900 to 1000 foot per second with a 180 grain slug out of a 2 inch barrel. This compares favorable with the .45 ACP round which does 850 foot per second with a 230 grain slug out of a 4 inch barrel. In short, the tiny Taurus 405 hits nearly as hard as the big Government Model .45 automatic.
Was it me, if I wanted a belly gun that hits harder than .38 Special, I'd look for one in .44 Special, or .44 Magnum, both of which are revolver cartridges with rims, so I don't have to mess around with half moon clips.
The Taurus is a throwback to the old Smith & Wesson .45 cal model of 1917. The Smith was an ordinary service revolver chambered for .45 ACP. The idea was an Army revolver that could fire the standard Army pistol cartridge, .45 ACP. It made partly for Army officers who didn't like the new fangled .45 automatic, and partly 'cause Smith could make revolvers all day when the makers of the .45 automatic were falling behind wartime demand.