Through a very recent experience to have a 10mm Mp5, I've learned the hard way that the .40/10mm kits produced by that certain "someone" have issues. I'll be replacing some of the expensive parts that I already thought i had. I don't want to get into a pissing match, just be aware that you may be replacing parts if you buy one of the .40 "kits" that isn't a true HK demill. The chamber in my 10mm barrel was cut too shallow and too wide. The cartridge clunks from side to side when you wiggle the barrel.