Another “known” issue seems to be steel and aluminum cased ammo binding in them. I’ve seen that reported with ETS mags also. Possibly something to do with the metal casings against the polymer body. Seems to be associated with leaving the magazines loaded for a while. I’m testing that out by leaving four PMAG 21s and an ETS 31-round mag loaded with Monarch steel and Federal aluminum for a month or so.
I took my PMAGs and one ETS 31-round magazine to the range yesterday and tested them out after they sat for a month loaded with a mix of Federal Aluminum 115 gr and Monarch steel cased 115 gr. I experienced several malfunctions, but I'm not sure that I can attribute any of them directly to the magazines. I'll describe them and see what you all make of them. I used a new (2016) Gen 3 Glock 19 that had 600 rounds through it prior to this outing. The mistake that I made was that I hadn't shot these two types of ammo through it prior to today, only Federal brass, Winchester, and Independence, so I can't say if it would feed aluminum or steel ammo with Glock factory mags.
I had three light primer strikes with two 50-round boxes of the Monarch ammo (both from the same lot). I guess calling them "light" isn't accurate, because they were fully dented by the striker, they just failed to ignite. All three fired on the second attempt. That's the last time I buy that junk ammo. I had two failures to eject and one failure to extract with the Federal Aluminum. The first malfunction was pretty strange, and I unfortunately didn't think to take a photo. I was firing a PMAG 15 with an alternating mix of Monarch and Federal (just for kicks), and an aluminum casing stovepiped on the second round. What was strange was that the casing jammed the slide open behind the fully chambered, unfired third round. I've never seen that before and am not sure how it happened. It's possible I may have kind of limp-wristed that shot though. I just adjusted the rear sight, which was pushed too far to the left, so I was kind of awkwardly resting my elbows on the range table (which was too low) to test the accuracy on my first couple shots today.
The next malfunction happened with Federal Aluminum in a PMAG 21. The casing failed to fully eject and jammed the slide open as it was feeding the next round:
The last malfunction was with Federal in a different PMAG 21 (I have them numbered). The casing failed to fully extract and created a double feed:
I'm not sure if any of this could have been caused by the PMAGs - they do have pretty strong springs that might have been forcing the next round up against the casing as it was extracting, but I'm not sure if that's possible. I would estimate that all of these four PMAG 21s have been fully loaded and shot about a 5-10 times each, and the PMAG 15 about 25-30 times.
Going forward, I'm going to test this G19 with Federal Aluminum in factory mags just to see if it malfunctions. I've never had issues with these Glock PMAGs using aluminum ammo in my other G19, but I haven't left them stored like this before - just loaded them at the range and fired them immediately. I'll continue to shoot brass cased ammo out of the PMAGs, and I feel comfortable with their reliability using that kind of ammo. I don't plan to use them as carry mags - I stick with factory mags for that - but I like having the PMAG 21s around for "emergencies."