.38 Long Colt: Difference between revisions

The .38 Long Colt's predecessor, the [[.38 Short Colt]], used a [[heeled bullet]] of {{convert|130|gr|g}} at a nominal {{convert|770|ft/s|m/s|abbr=on}}, producing {{convert|165|ft·lbf|J|abbr=on}} [[muzzle energy]]. The cylindrical "shank" or "bearing surface" of the bullet, just in front of the cartridge case mouth, was {{convert|.374|or|.375|in|mm|2|abbr=on}} in diameter, the same as the outside diameter of the cartridge case (as in [[.22 Long Rifle|.22 rimfire]] cartridges). A smaller-diameter portion of the bullet, the "heel", was crimped inside the case mouth, and the lubricant was outside the case, and exposed.{{efn|This practice evolved as a way to convert cap-and-ball .36 caliber [[Colt 1851 Navy Revolver|Navy revolvers]], which had cylindrical or single-diameter "charge holes", or firing chambers, into cartridge arms.}}

In contrast, the .38 Long Colt uses a {{convert|.357|–|.358|in|mm|2|abbr=on}} bullet, the bearing surface and lubricant of which are entirely contained within the cartridge case. This kept the waxy lubricant from collecting grit which can damage the revolver's barrel. Colt, however, retained the single-diameter charge hole, resulting in the bullet failing to form a seal as it traveled through the chamber throat. This seal was expected to cause the bullet to expand in the throat and be "[[Swaging#Firearms|swaged down]]", or reduced again in diameter, as it entered the barrel, but uneven expansion producingproduced poor accuracy.

In the [[United States Army]]'s original black-powder cartridge used by the Model[[Colt 1892M1892]] revolver, muzzle velocity from the revolver's {{convert|6|in|mm|adj=mid|-long}} barrel was {{convert|708|ft/s|m/s|abbr=on}} with a bullet weighing {{convert|150|gr|g}},<ref>U.S. Army Ordnance Department (1893), p. 241</ref> resulting in a muzzle energy of {{convert|167|ft.lbf|J|abbr=on}}. Later, the Army changed its cartridge to [[smokeless powder]] and slightly tightened the revolver's [[Gauge (firearms)|bore]]; the new muzzle velocity was {{convert|750|ft/s|m/s|abbr=on}} with a bullet of {{convert|148|gr|g}},<ref>U.S. Army Ordnance Department (1917), p. 12</ref> giving a muzzle energy of {{convert|185|ft.lbf|J|abbr=on}}.