First Gen Colts were chambered for a bewildering number of cartridges. Yes, 45 Colt was first in 1873 and 44-40 followed in 1878. These were the two most popular chamberings, Colt made 158,885 First Gens chambered for 45 Colt and 71,391 First Gens chambered for 44-40. However, the list of cartridges First Gens were chambered for is 22 Rimfire, 32, Rimfire, 32 Colt, 32 S&W, 32-44 S&W, 32-20, 38 Colt, 38 S&W, 38 Special, 38-44, 357 Magnum, 380 Eley, 38-40, 41 Colt, 44 Colt, 44 Smooth Bore, 44 Rimfire, 44 German, 44 Russian, 44 S&W, 44 Special, 44-40, 45 Colt, 45 Smooth Bore, 45 ACP, 450 Boxer, 450 Eley, 455 Eley, & 476 Eley.