I just know when I tried to use the 10 on the USP .45 and the USP .40 things felt ****y and weird, and I had light strikes with some kinds of ammo.
interesting because on the HK forums it looks like the people who encountered issues it was mostly with the USP 45. i can't think of any reason for this as they all use the same OEM hammer springs, unless there's something dimensionally unique about the USP 45.
http://www.hkpro.com/forum/hk-handgun-talk/74038-wolff-springs-11.html
i'm going to hold off on calling the 10# hammer spring truly "reliable" until i put another 1k rounds of various ammo, especially stuff w crappy russian primers.