just got back from the range and my hk51 with the .22 conversion finally broke. this has been my test mule for the .22 hk drum adapters as most will recall. the extractor broke at about 225000 rnds and had to be replaced. last thursday after over 600000 rnd s of .22 f/a the firing pin and the little spool that holds the uclip in broke. interestingly enough the gun was still running perfect but the firing pin would occasionally stick out of the bolt about 3/8ths of an inch ! i ran 4 drums flawless with it after it broke amazingly enough . a couple of new parts from another conversion unit and we are ready for another 600000 rnds !!!