I got some 9x18 Mak ammo from Underwood Ammo recently and put it through a little T&E and it seems to be pretty good stuff. It's loaded with the 95gr Hornady XTP bullet and the advertised velocity is 1150fps.
Before I go on, let's address the pressure issue. There were several Russian 9x18 rounds developed over the years of various weights and pressures, most ranged between 20,000 and 24,000 PSI. The Czechs designed a 69gr load in the early 1980s that traveled at 1350fps out of their CZ 82s that had a chamber pressure of 24,650 PSI. The ammo being reviewed today has a chamber pressure of 24,500 so it's actually slightly under what the Czechs used as their service round for the last few years that the gun was in service. After firing this ammo, I didn't see any evidence of stressed cases (bulges, cracks, ect...). As to whether other 9x18 guns can run this ammo as effectively and safely, I can't say for certain but most probably can since Russian put out a couple loads around 24,000 PSI and they were used by seveal nations in their guns.
Moving on.... With 9x18 guns, people often debate whether one should use JHPs or FMJs for defensive purposes. With that in mind, the XTP bullet may be the ideal compromise. XTPs are known for relatively deep penetration due to relatively small expansion between 1.25-1.50x the original diameter once it meets soft tissue.
Here's a video with of me running some rounds through my CZ, a quick discussion of the rounds charachteristics, and a chronograph test comparing the Underwood load with the factory Hornady load:
Underwood 9x18 Mak HD Review Video Link
Underwood 9x18 95gr XTP: 1198fps, 303 ft/lbs energy at the muzzle
Hornady 9x18 95gt XTP: 999fps, 210 ft/lbs energy at the muzzle
This round should be availible shortly on the Underwood site for those looking to pick some up.