One of the first was a cartridge used in one of the most pivotal arms in American history--the Henry rifle. The cartridge is a rimfire called the .44 Henry or .44 Henry Flat. It's a true .44 with a bullet diameter of .446-inch and a case length of .875-inch. The long under-barrel magazine tube of the Henry held 15 of these stubby rounds, which were also used in the later Winchester '66 rifles and carbines. Colt made the 1872 Open Top and about 1,800 Peacemakers in the caliber and S&W produced a special rimfire version of their big No. 3 breaktop for the Turks. The same ammo worked in rifle and revolver, which marks the first use of the same ammo in both.