"In 1937, while preparing for the National Matches, I developed the .221 Askins. This was a .22 caliber automatic which fired a .22 centerfire ctg. The NRA rules in '37 stipulated that "any centerfire caliber" could be fired in the Nationals. At that time the only useable centerfire cal was limited to the revolvers. You could fire the .32 S&W long which was the smallest caliber and one yet accurate enough to compete with. I concluded if I could develop a .22 centerfire I'd have the boys over a barrel."
"The .221 Askins was the 5.5 Velo-Dog ctg shortened in length to exactly the .22 long rifle casing; the bullet was the standard .22 long rifle leaden slug at 40 grains. The Velo-Dog was designed to be fired in a French revolver; it had a rimmed casing. My gunsmith and I ran every case through the lathe and reduced the diameter of the rim to the same specs as the .22 long rifle rimfire shell."
Whole thing here.