.400 Cor-Bon

Peter Pi of Cor-Bon designed this round in 1997 by necking the widely available .45 ACP case down to a .40-calibre bullet at a 25-degree shoulder, deliberately basing it on the most common pistol brass in American circulation so handloaders would have an ample and cheap supply of cases. His stated aim was higher velocity for a hollow-point bullet than .45 ACP itself could produce, on the reasoning that a faster bullet expands more reliably at the target.

Its practicality lay in how little a .45 ACP pistol needed to change to fire it: because the case shares the same base, rim and overall length as its parent, most existing .45 ACP handguns could be converted with a drop-in barrel alone, keeping the same magazine, guide rod and extractor. Some 1911-pattern pistols needed only a heavier recoil spring to cycle reliably.

No C.I.P. or SAAMI dimensional standard has been located for this cartridge, so every figure here is converted from the Wikipedia infobox’s own Cor-Bon ballistics data and carries estimated status. No test-barrel length is published for any of its three loads, so only bullet mass is recorded for each, and no photograph illustrates this entry.