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 Walker was largely built from leftover Walker parts. Subsequent contracts beginning in 1848 followed, for what is today known among collectors as the First, Second and Third Dragoon Models that were all based on the Colt Walker, enabling a rapid evolution of the basic revolver design. These improvements included shorter barrels, shorter chambers, typically loaded only to 50 grains instead of 60 grains, thereby reducing the occurrence of ruptured cylinders, and the addition of an improved catch at the end of the loading lever to prevent the dropping of the loading lever under recoil. The Colt Walker was quite powerful, with