What type chamber do you have? If a match chamber only run very good ammo thru it, if a standard chamber you can run just about anything, doesn't mean it will be accurate. For accuracy the better the ammo the more accurate.
I worked with the armorer for the PD (I'm the SO armorer) to get to the root cause. Almost assuredly it boils down to mixed brass (Commercial and Military) of unknown origin and history that was not processed properly.
We found several loaded rounds that were out of specs. The case (mostly Military) had not been trimmed and was likely fired through a SAW or had been fired several times with out being trimmed. When the brass gets too long, the mouth will be forced into the rifling thus not allowing the bullet to leave until the pressures go WAY up. In internal ballistics bad things can happen in milliseconds.
This combined with the smaller internal dimensions of the military case (brass is thicker) and a powder charge that is at or near max for a commercial case will cause pressures to skyrocket.
The variance between manufacturers of brass can cause accuracy problems but the Military cases are in a different league. That is why every manufacturer of reloading components recommends working up a new load when ANY component is changed.
For Pete's sake, don't shoot Wolf in a US/ Euro model gun. It is the dirtiest, nastiest stuff you can buy. The cases are brutal on extractors that are designed for brass. The only thing I would recommned Wolf for is Anything Kalishnikov (AK) . Wolf has a gold line, but I will bet you a beer that the same powder goes in that brass case as does the steel stuff. Did I mention it is the dirtiest ammo I have ever used?
Any quality production ammo is OK. I have read more than one bad experience with WWB ammo though. I used to shoot it because of the price, but now it has gone way up too (Wal Mart).