.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 (4.5 mm) bullet. Initial loadings will be a 20 grain bullet, delivering muzzle velocities around 3000 ft/s.

Development
Winchester, in conjunction with Savage Arms (manufacturer in the rimfire rifle market), introduced this cartridge at the 2013 SHOT Show.

The brass case for this round is roughly 50% thicker than the 17 HMR, and the max average internal pressure is 33,000 psi, versus the 17 HMR's 26,000 psi.

Availability
As of January 2013 some retail outlets are listing the ammunition with expected availability of late first quarter or early second quarter 2013. Hornady will also be delivering a 25 grain V-max loading at 2,600 fps. Currently, Savage is the only company offering a rifle in this caliber, with the B-Mag