Huh. Interesting. Ive used GL9 mags in my 19 extensively and never had a single problem. You have 15 mags and 87% (giggidy) had problems? That is a pretty ridiculous accusation.

I think your English fails you.   It’s not an accusation, it’s an observation.  Seems that I’m not alone.  Thanks for reporting.

I started an experiment today. I loaded up two PMAG 21s with Federal aluminum 115 gr FMJ and two with cheap Monarch 115 gr steel cased FMJ. Just for fun, I loaded my one PMAG 15 with alternating Federal and Monarch rounds. I’m going to let them sit for a few weeks and then see how they function. I’m really not a fan of Monarch ammo, but it was the only steel cased ammo I could find in 50 round boxes. I didn’t want to buy 150 rounds of the Winchester version.

I did notice just while loading the Monarch ammo that it seemed to get kind of stuck, like the last few rounds were nosing up despite all the spring pressure under them. It felt different from loading the Federal aluminum, maybe because of the coating on the steel casings.

I took my PMAGs and one ETS 31-round magazine to the range today 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 - a Lipseys full FDE model - 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."

Mine have been straight garbage with steel case. Sometimes I can't load them to full from binding up. Will also notice round on top having no tension often allowing it to fall out.

I was fully expecting to have some kind of issue with the steel cased ammo based on all the reports, but I didn’t run into any problems today aside from the primer failures. They fed fine and didn’t seem to bind or stick at all. I’m going to avoid using steel ammo in my PMAGs (and probably my pistols in general) anyway though.

Measure the rim diameter on the aluminum case.  I've been seeing some reports of that ammo and FTEx lately online.

My Pmags have been doing fine with brass cased round nose.  They're reliable enough for me to use at matches, so they're ok.   I still wouldn't carry one on a dare though!

I’ll check the casings out when I buy another box of that stuff. Thanks for the tip.

I guess it’s too much for us to ask for Glock to produce their own 21-round 9mm mag...

I have 6 (4 15 and 2 21s).  Had sticking issue on 3 of them with blazer aluminum only.  Emailed Magpul - they recommended CLP cleaning but also offered immediate replacement.  After 1 CLP cleaning never had a issue again - brass, steel, nor aluminum

Most of the problems with non-brass cases?

Seems that way.