As early as 1915, S&W was redesigning the 455 Hand Ejector to handle the 45 ACP cartridge. Chambering and firing the cartridge was really no problem. The hitch was ejection. The extractor slid right past the rimless case. S&W came up with two fixes, both clips. One held six rounds and the other held three. The Military realized Colt’s could not produce enough 1911s to satisfy the demand and turned to S&W to help. Given their choice, the Army board accepted the 45 ACP Hand Ejector and the 3 round clip. S&W allowed Colt’s to use the clip without royalty or infringement. (During the ACW S&W controlled the bored through cylinder patent and would not allow it’s use without suit. This, in the opinion of U S Grant extended the length of the war and caused more casualties. He held that against S&W. When President, Grant was not kind to S&W. S&W did not want to repeat history.).
Initially Colt’s did produce some revolvers with bored through cylinders. Not many and the majority had the cylinder replaced with a proper one either at the factory or by Unit Armorers.
Kevin