The .221 Askins

Back in 1937, Col. Charles Askins, who was then in the US Border Patrol, was looking for a way to improve his centerfire Bullseye pistol scores. He experimented with a number of wildcats based on shortened .380 cases, various .32s, the .25ACP, and others, trying to create a round that was accurate and as low in recoil as the .22LR. Then one night on patrol he intercepted a smuggler carrying an old 5.5 Velo Dog pistol like one of these:

These were cheap revolvers that originated in France, intended for bicyclists as a defense against against dogs attacks. They fired a curious centerfire cartridge, the 5.5 Velo Dog, that was similar in size to the .22LR, but much longer- and it was a centerfire cartridge:

The Velo Dogs were loaded with a jacketed bullet, as opposed to the heeled lead bullets used in .22 rimfire cartridges. The bullet diameter was the same as the standard .22, but the case diameter was larger than the bore, like most modern cartridges. Although longer than a modern .22LR, they were less powerful. The Kynoch load generated 42 foot-pounds of muzzle energy, and the domestic Remington load, 55. 

Askins managed to buy up or otherwise acquire several thousand rounds of of these obsolete cartridges. He pulled the bullets on several hundred, and shortened them on a lathe to .22LR length. He then found a supplier of lead bullets in the correct size, a set of reloading dies, and had one of his Colt Woodsman pistols modified to take the new cartridge, which he dubbed the .221 Askins. His load was a cast lead semi-wadcutter over about 1.5gr of Bullseye or DuPont #5, depending which version of the story you read, and with it he won the All-Around pistol championship in 1937. Following that match, the NRA amended the "any centerfire" pistol rules to read "any centerfire (.32 caliber and above.)"

Footnote: Askins was not the first to produce a wildcat based on the .22 Velo Dog. According to J.J. Donnelly's 1987 The Handloader's Manual of Cartridge Conversions (Revised Edition), there was a .14 Velo Dog produced by necking down the Velo Dog. I don't think there's ever been a commercial .14 caliber cartridge, but the caliber is popular with some wildcatters.

As of several years ago Fiocchi was still loading the 5.75mm Velo Dog; I don't know if it's still available in Europe; I couldn't find any domestic suppliers with new stock.