7.5 FK

The 7.5 BRNO was developed between 2009 and 2014, for the specific purpose of providing high capacity automatic pistols the ability to engage combatant targets at a range of between 75–150 metres (246–492 ft) while retaining more kinetic energy at that range than what a 9×19mm Parabellum cartridge can generate at the muzzle/point blank range.[2]

Initially, it was chambered in the all-steel FK BRNO Field Pistol which has a unique patented recoil attenuating system but subsequently FK BRNO developed a polymer version of that that design designated as the FK PSD. [3]

The 7.5 FK has 1.50 cm³ (23.21 grain of H2O) cartridge case capacity.

7.5 FK maximum C.I.P. cartridge dimensions[1]

Americans would define the shoulder angle at alpha/2 = 30 degrees. The common rifling twist for this cartridge is 270mm (1 in 10.62" inch), 6 grooves, Ø lands = 7.5 mm, Ø grooves = 7.77mm, land width = 3.75 mm, and the primer type is small pistol.

Contrary to some published information, this cartridge is not based on a necked down 10mm Auto case, and hand loaders cannot and should not attempt to make a 7.5 case from a 10mm Auto case, as the case is longer, thicker, and operates at significantly higher pressure. Therefore, necking down and stretching the 10mm Auto would create much thinner walls at the critical shoulder/neck area and can potentially be very dangerous to the user.

According to C.I.P rulings, the 7.5 FK case can handle up to 350 MPa (50,763 psi) piezo pressure. In C.I.P regulated countries every pistol cartridge combo has to be proofed at 130% of this maximum C.I.P pressure to certify for sale to consumers.