I have a usp 40 with ke 1994 dare code, I haven't ever shot it much because I only had one mag with it, I've recently got it our and started shooting it lately and have noticed a few concerns that makes me think I should send it in for service. I searched and could only find info on full mag, my question is this, when I shoot 9 rounds the last 10th round is usually not going into battery, I've had two live round stove pipes and several spent round hangups. Never thought I'd see malfunctioning in this pistol but it happens I guess, I believe it's due to a worn out magazine or spring, my main concern is when the slide is locked back from last round, I can release the mag and my slide automatically goes to battery every time, is this normal? Or should I call customer service for a checkup? Also, I can't find my receipt, how hard is it to get my gun fixed by hk without proof of purchase?