In late 1969 Colt began investigating a possible replacement for the M1911 pistol, one that they hoped to eventually sell to the military. The idea was to develop a completely new weapon, one capable of a high rate of semi-auto or burst fire, lightweight, compact, and accurate, both an offensive and defensive machine pistol. The prototype was dubbed the SCAMP, for Small Caliber Machine Pistol.
To meet the criteria in a high capacity handgun required a small cartridge. Colt considered a variety of existing cartridges ranging from the 5mm rimfire all the way to the 5.56x45. They selected the 221 Remington Fireball as a starting point but even it proved to be too hot, with too much recoil for a machine pistol. They finally settled on a modified 22 Hornet case with a 40 grain bullet. The first cartridges used re-formed Hornet cases and commercial bullets and once the desired ballistics were confirmed a contract was let to IVI for 1000 new cases and bullets. Colt loaded the ammunition which was tested in the sole prototype pistol. Even though the test results were mostly positive the project never moved beyond the prototype stage.
There is much confusion over the SCAMP cartridges primarily because the USAF was investigating a similar concept using their own IMP (Individual Multi Purpose) weapon firing the 221 IMP cartridge, which was an unmodified 221 Fireball. Some of todays Internet sources describe the SCAMP as