The 451 Detonics was developed by the Detonics manufacturing co. in the early 1980’s in the search for a more potent version of the M1911. To achieve this they used a shortened .45 Win Mag cases that had a much stronger base in their Combat Master pistol, basically a 45 Win Mag case shortened to fit in a 1911 magazine but the 451 Detonics case is longer than the standard 45 ACP so that it will not chamber in a standard 45 ACP, although the overall length is the same as the 45 ACP. It is therefore able to handle much higher pressures than a normal 45 ACP. The original cases were manufactured by Winchester. (Erlmeier, Brandt Ref. 454A – See Erlmeier Brandt Vol. 3 p. 113).