38 Long Colt—a smokeless-powder cartridge with roughly half the striking energy of the .45 Colt. During the Philippine Insurrection, the Army realized its new sidearm’s shortcoming ...

45 ACP (Automatic Colt Pistol) cartridge, it became the U.S. Armed Forces’ standard-issue sidearm following the failures of the Army’s .38 Long Colt revolvers during the fight against the Moro ...