.17 Winchester Super Magnum

.17 Winchester Super Magnum, is a rimfire rifle cartridge developed by the ammunition company Winchester in 2012. It descended from the .27 caliber nail-gun blank by necking down the blank case to take a .17 caliber bullet. Initial loadings were with a 20-grain bullet, delivering muzzle velocities around 3,000 ft/s. Wikipedia
Bullet diameter.172 in (4.4 mm)
Case length1.200 in (30.5 mm)
Parent case.27 caliber nail gun blank
Overall length1.440 in (36.58 mm) to 1.590 in (40.39 mm)