I had a piece of brass get caught lengthwise between the breechface and the barrel hood. I've never seen that happen before, and I've never had a malfunction with the stock plastic guide rod. In case anyone is wondering, the ammo was Remington UMC and the spring was an almost new ISMI 17 pound spring. There is no other aftermarket stuff in this G17. I've run several thousand rounds through my other G17 with a Lightning Strike captured guide rod with no problems. That one came with a washer to keep the spring from crawling past the screw. The ISMI rod in question didn't have a washer. I don't know if that has anything to do with it or not. I've put the stock rod and spring back in.