Colt Walker of Texas had been the major purchaser of the early Paterson Holster Pistol (No. 5 model), a five shot cal .36 revolver, and Samuel Walker became familiar with it during his service as a Texas Ranger. In 1847, Walker was engaged in the Mexican-American War as a captain in the United States Mounted Rifles. He approached Colt, requesting a large revolver to replace the single-shot Aston Johnson holster pistols then in use. The desired .44-.45 caliber revolver would be carried in saddle mounted holsters and would be large enough to dispatch horses as well as enemy soldiers. The Colt Walker
Colt 1851 Navy Revolver major success in the gun trade; the naval theme of the engraved cylinder of the Colt 1851 Navy revolver was Colt's gesture of appreciation. The engraving was provided by Waterman Ormsby. Despite the "Navy" designation, the revolver was chiefly purchased by civilians and military land forces. The .36 caliber (0.375–0.380 inch) round lead ball weighs 80 grains and, at a velocity of 1,000 feet per second, is comparable to the modern .380 pistol cartridge in power. Loads consist of loose powder and ball or bullet, metallic foil cartridges (early), and combustible paper cartridges (Civil War era), all combinations being ignited