I just got my new HK USP Compact 9mm Variant I. It looks great, but it sounded like it had a loose piece rolling around inside. I field stripped it, and found that the culprit is a white plastic ring around the recoil spring assembly, which slides up and down the assembly. I checked the owners manual, and it appears that the ring is supposed to be there. My question is: is this normal? are the rings normally tighter so they don't slide back and forth? what should I do?