John Browning committed 20 years to long-gun design for Winchester. But he applied his genius to handguns even before Thomas Bennett at Winchester demurred on John's autoloading shotgun in 1900, ending the relationship. That year Colt manufactured John Browning's .38 self-loading pistol, the first of its kind built in the U.S.--though Browning had a working model ready in 1895.
Colt bought four pistols from the prolific inventor and based all its subsequent self-loaders on those designs. Among the most important features of Browning pistols was an operating slide mated to the frame by rails. The slide comprised action housing, sighting rib and bolt. It added mass to the recoil mechanism and permitted a range of chamberings--including Browning's own .25, .32, .380 and .45 ACP.
Browning thought his pistol had great promise as a military sidearm. In 1902 he developed a .38 called the Military Model. But the recent Moro insurrection in the Philippines had soured soldiers on the .38 Colt, which had failed to stop frenzied attackers.
Browning responded with two .45 caliber pistols, one with an exposed hammer, the other without. He marketed his exposed-hammer Model 1905 through Colt. To ensure his pistol was ready for Army trials in March 1911, Browning (with protÃ©gÃ© Fred Moore, chief of Colt's machine gun division) subjected a sample to a 6,000-round endurance run, in 100-shot stings. The gun functioned through an acid bath and a diet of dust and damaged ammo. Browning's homework paid off when the trials board recommended his .45 Automatic Pistol for service. It would stay there for half a century, through two world wars.