Ok .... This might be a really dumb question but I'm new to shooting. I have a new G17 that I have put about 200 rounds through without any problem. I went to the range today with my buddy who has a XDm 9mm. We both started shooting 115g 9mm and everything was ok. In my 2nd clip my 17 started to jam really bad. It wouldn't ejecting the shells. I didn't know what the problem was so I switched to a 124grain 9mm and it started to shoot fine. I was really confused why my G17 would only shoot 124g ammo. Then my buddy started to shoot his XDm without any problems, but in his 3rd clip his started to jam really bad also. He has a new XDm 9mm that he has gone through at least 1K rounds. We weren't using the same ammo either. It was very hot today. The heat index in Raleigh/Durham NC was over 110 degrees. Could the heat and humidity really cause our guns to jam like that? Is that why the 124g ammo worked and the 115g didnt'?