.221 Remington Fireball

Remington introduced the .221 Fireball in 1963 by shortening the .222 Remington’s case to 35.56 mm, purpose-built for the single-shot, bolt-action XP-100 pistol the company launched alongside it. Cutting the case down meant less powder capacity than the rifle round it was derived from, so Remington’s engineers raised the maximum average pressure to 52,000 CUP — against 46,000 CUP for the full-length .222 — specifically to limit the velocity lost to a handgun-length barrel.

The result was, and remains, one of the fastest handgun cartridges ever placed in commercial production, built around the idea that a short, high-pressure case in a long single-shot barrel could still deliver rifle-like performance from a pistol-length gun. It went on to be chambered in bolt-action and single-shot rifles as well as the Contender-pattern pistols it was designed for, serving both as a varmint round and as a platform for wildcatters, including the .17 Remington Fireball derived from it decades later.

No free SAAMI or C.I.P. dimensional standard was found for this cartridge, so its case and bullet dimensions here are estimated from a Thompson/Center reloading-data sheet published by Accurate Powder, cross-checked against the Wikipedia infobox figures, which they match. No velocity is recorded at all. The three bullet weights below are the ones that sheet is built around, but every velocity published for this cartridge that could be found is a handloading figure — the speed a particular charge produced at the top of a load ladder, which is a property of that recipe rather than of the cartridge, and which this site does not record. Factory-ammunition velocities with a stated test barrel, the kind recorded everywhere else here, were not found. No maximum pressure is recorded either: the only figure found is in CUP, a pressure-testing method with no fixed conversion to the pascal-based figures this site stores, and converting between the two would be presenting an estimate as a measurement.