IIRC, neither the Steyr GB nor the H&K P7 were intended as military service pistols, they were entrants in a competition for a 9mm police pistol. For some reason, the specifications requested a fixed barrel, hence the odd-ball designs.
I have a GB, the American-made Rogak copy, and an H&K P7. I don't like any of them; the Rogak is junk, the GB far too big for a reasonable carry pistol, and the H&K an over-engineered clunker, albeit one with a cult following. Actually, the piston system of the P7 is not bad - it is that silly squeeze cocking that I detest because if the shooter relaxes for an instant, he then must fight the cocker to put the pistol back in operation. I can't imagine why NJ ever adopted it for their State Police, unless something else (who knows what?) tipped the scales.
In addition to those pistols, there was also the Walther PP Super (a scaled up PP), made for the other 9x18, the 9x18 Police. The idea was the same, as powerful a round as was reasonably possible for a blowback (fixed barrel) pistol. But recoil is heavy, as it is in the Makarov, and that idea also never got very far although some German state police adopted the Walther.
Jim