Ok, I'm not an armorer, but I am not exactly new to Glocks (I've lost count to how many I own) but this one's got me stumped.
Fairly new Glock 20 with maybe 500 rounds through it. The only thing I did with this gun is install a 22 pound recoil spring at the suggestion of Mike from DoubleTap to run his ammo. Otherwise it is all factory.
I've run a mixture of about 300 rounds of 135 grain DoubleTap and and 200 grain Beartooth DoubleTap loads without any problems. (The 135's were a bit hot, though) I've also run several boxes of Blazer without issues.
I started to get this malfuntion when trying DoubleTap 155 and 165 grain Gold Dots. Out of 100 rounds I had 5 of these malfuntions that a usual tap and rack would not clear.
Sorry about the crappy cell phone pics. It's all I had at the range yesterday.
For what it's worth, it did it with the 22 pound recoil spring and the factory recoil spring in it, too. It also did it with and without the light hanging on it.
I am not set up to load 10 mm, yet, and factory ammo is getting way too expensive to trouble shoot a gun these days.
Any ideas?