380 ACP and a 9mm. Of course, the longer the barrel, the better the performance. High-pressure .38 Specials can perform pretty well from a carbine barrel, which is cool if you have a lever gun ...
45 caliber. After the 1911, he never built another gun chambered in .45 ACP. Looking at his other famous handguns: the Colt 1903 Hammerless was in .380 ACP, the Colt Woodsman was a .22 LR, and the ...