.22 Short

.22 Short is a variety of .22 caliber rimfire ammunition. Developed in 1857 for the first Smith & Wesson revolver, the .22 rimfire was the first American metallic cartridge. The original loading was a 29 or 30 gr bullet and 4 gr of black powder.Wikipedia
 
Bullet diameter.222 in (5.6 mm)
Rifling twist1-20" or 1-24"
Case length.421 in (10.7 mm)
Overall length.695 in (17.7 mm)
Rim diameter.278 in (7.1 mm)
Base diameter.226 in (5.7 mm)
Neck diameter.226 in (5.7 mm)