I've seen a lot of threads about adding this part and that part with the caveat being to always make sure of your part count to remain 922r compliant. Is this much of a concern with PTR rifles and furniture? They used to offer some of their rifles with the collapsible stock (they don't anymore) which I assumed was an original HK stock. So one might assume that installing one on a PTR that didn't come with one would be okay. But did the PTR rifles with the collapsible stocks include more U.S. made parts elsewhere in the rifle to remain 922r compliant? What about wide HK handguards?