This is possible. Since the Glock 27 has space on the grip for only two non-trigger fingers (middle and ring), I usually rest my pinky finger on the very bottom of the stock magazine (which would be about 3/4 of an inch from the bottom on the 15-round magazine that I'm having issues with). I'll test that theory out next time I go shooting and see if leaving the pinky finger off of it makes any difference.I have a G26 and a G27, both of which are gen3's, and though I don't shoot them very much, neither one of them have ever had any problems of any kind whatsoever. I installed a Pierce mag extension on both or their primary magazines to allow my shooting hand to gain a better purchase on the guns. In your case, I am leaning towards one of your hands contacting your larger magazine at the time of firing. I know I had something like this happen to my primary carry gen3 G23 (was shooting from a rest once and the recoil apparently caused the magazine to seat deeper into its well causing a stovepipe). In particular, I would bet one or both of your hands is causing the larger magazine to bend towards the backstrap at the moment of firing. This would be a natural thing since recoil pushes the gun up and back.
Well, unfortunately, as I mentioned earlier, I have very small hands for a man. More specifically, my hands are basically the size of a girl's hands. According to this website (http://www.celtarts.com/ring_size.htm), my hands, using my right ring finger size (6.75) as a proxy, are closer to a woman's average hand size (7) than a man's average hand size (10). So, any issues with "girls commonly limp-wristing a Glock", perhaps due to smaller hand sizes, may apply to this situation.The only FTF issues I have seen with Glock 27 and 17's is from limp wristing. In both cases they were girls. The first one has gotten lots of training and now fired a couple thousand Rds and no longer has the issue. The second I'm working on. Not to say there can't be other causes. But they are very reliable feeding arms.
It is a Glock 22 magazine. The magazine has holes to indicate 15 rounds, not 17; the rear side of the magazine has the inscription ".40" at the top; and the top of the magazine towards the rear has the inscription ".40" (although, interestingly, the front of the top of the magazine, where the magazine contacts with the slide stop, has the inscription "9.", just like my stock 9-round magazines).since you said it was new i would check and insure you in fact got a g22 magazine and not a g17 magazine. they can be easily mixed up just by glancing at them