Greetings. My wife recently purchased a Glock 20 Gen 4 as a wedding gift for me, and before I brought it to the range, I decided I would purchase a G19 as well. I spent a good amount of time looking over and dry firing both before I had time to test them out. They both had a slide to frame fit comparable to my other dozen pistols, and were near identical to each other. Last week I brought them both to the range, and put around 250 rds through the 19 and 100 rds through the 20. When I looked them over it home, I noticed the 20 become pretty loose. The rear of the slide clicks back and forth when I put lateral pressure on it, and it rattles around now (not the firing pin rattle) quite a bit, be it cocked or not, with or without magazine, and with or without a snap cap in the chamber. For polymer pistols, I have an HK P30, USP 45T, Walther PPS, & a FiveseveN. None of these are as close to being as loose, regardless of the amount of rds through them. I read a few posts about Gen 4 21s being loose, but what sets my case apart is that before I fired it, it was pretty tight. Now it rattles like a can of krylo n, while the 19 seems just as before. My 1911s and SIGs loosened a little after a lot of rounds, but this is a night and day difference. Does this seem normal? Thanks in advance for your input.