A friend brought this to my attention recently.....it's currently a proprietary round developed by Cz, the 7.5 FK BRNO.
It not based off any current cartridge, but it kinda reminds me of a revamped updated supercharged x25 Tokarev. :)
It's basically a 7.8x27mm, roughly a .30 cal 100 grain bullet, that goes 2000fps and almost 900ft lbs of muzzle energy, measured from their handgun.
http://www.fkbrno.com/en
http://www.fkbrno.com/en/7-5-fk-system
http://www.gunsholstersandgear.com/2016/07/19/worlds-fastest-handgun-not-7-5-fk-brno/
That's pretty cool! A bottle necked cartridge of 7.5 x 27 versus 7.62 x 25 sounds similar to me. Definitely hotter than the Tokarev. Those Czechs of Brno are at it again thumb1