The 45 Winchester Magnum was introduced by Winchester in 1979. It is a powerful rimless cartridge using a .452-inch bullet with a case length of 1.572 inches. With a breech pressure about double that of the 45 ACP it propels heavier bullets at higher velocity--a 320-grain bullet at 1150 feet per second, yielding nearly 1000 foot-pounds of energy (double the 345 ACP). Originally designed for the Wildey pistol, financial difficulties precluded production and semiautomatic pistols 45 Winchester Magnum pistols have not been available. Thompson/Center offered it in Contender barrels and it proved an effective handgun hunting cartridge in that platform. Despite excellent performance the 45 Winchester Magnum is lapsing in near-obsolescence and seems unlikely to make a resurgence. -- Craig Boddington