Decided to grab a few cheap mags for my Glock 19 just for plinking around at the range.  I've seen a lot of good reviews for these KCI mags as well as a few bad ones but figured that for $10 each I might as well try them.  I had no problem loading the mags to capacity and they freely fell from the gun when released.  At the range I found that if the slide was in the locked back position and I tried to insert the mag and release the slide by pulling it back and then releasing the first round would consistently jam, an issue I do not have with the factory mags.  If I released the slide by using the slide release the first round would not jam.  Beyond that they functioned flawlessly.

I have 15 of em. Never had an issue. I seen em as disposable assests.

I never had any issues with them in my glock but they jammed up in my sub 2000 constantly.