Problems with Gen3 Pmag 20 5.56X45

[mjh30]

Since I never used a couple I had on hand before today, I never realized there was a problem with them (some of them). Obviously I searched (googled) and found some postings with regards to said problems and how Magpul had discovered there was an issue (stacking tolerance) and was addressing it. I suppose I am just posting this because these were a few of the mags that I kept loaded and lying around. I guess I should have checked to see if they worked in my rifle first. Anyways Magpul is going to change out the ones that don't work for new production mags.

 

[LRRPF52]

Did you have any malfunctions, and if so, what did they manifest as?

 

[rjacobs]

Yea what issue did you have?

I have several of the 20's(gen 1 or 2, definitely not gen 3) and most fail to lock the bolt back on the last round. They are bench or training mags for me anyhow.

 

[mjh30]

Insert mag on closed bolt, mag appears locked in, rifle would function normally for a few rounds, then click empty chamber. Basically mag did not seat right on closed bolt. They stopped making the gen 1 and 2's for that very reason,
posted my Magppul in September
There was a tolerance stacking issue in the initially released magazine, that in some magazines, when combined with some ammunition types, created a condition where the second round could nose up alongside the first. This condition required a bunch of things to line up to manifest itself, but it existed, so we're fixing it. It's innocuous enough that you may not even notice it even if it is occurring with your setup. It doesn't affect feeding at all, just seating force on a closed bolt. If inserted into a firearm with the bolt open, the condition self corrects, and the magazine feeds 100% normally. Some lowers do not allow seating on a closed bolt with this condition manifesting, however, or require a significant increase in seating force. Once the magazine is seated, however...once again, it feeds normally. We identified and implemented a fix, and are finishing up testing on that fix right now. Once we start production again, owners of existing 20 rounders will be able to swap them out if they are experiencing the issue, or just to be sure, and the new 20s going forward will, of course, not have the issue.

 

[-Nick-]

I thought I was the only one allowed to have broken shit around here MJH? Lol...

 

[bobke]

Not certain if this might be an/the issue, but had trouble with 3 brand new Gen3 mags in one of two AR's I'd run them in. The small shoulder on the mags that sits up against the front of the trigger guard and acts as a stop was a bit thick and impeded full entry of mag in lower. Few minutes with a Dremel fixed it by slicing off about half the original shoulder. This with the Magpul enhanced finger guard on the lower in question. All said, pays to test all your mags before heading to the range with mags you felt certain would function. These wouldn't even seat in magwell. All that said, wonder if your mags aren't seating fully home and causing a FTF issue.

 

[WaveNature]

Insert mag on closed bolt, mag appears locked in, rifle would function normally for a few rounds, then click empty chamber. Basically mag did not seat right on closed bolt. They stopped making the gen 1 and 2's for that very reason,
posted my Magppul in September
There was a tolerance stacking issue in the initially released magazine, that in some magazines, when combined with some ammunition types, created a condition where the second round could nose up alongside the first.

Very interesting. I think this is the reason I was getting double feeds with my gen2 20rnd Pmags. If I had one in the pipe and 20 in the mag, the third and fourth round would double feed. Loading them to 19 seemed to fix the problem but they fail to lock the bolt every once in a while like rjacobs' mags. I wonder if the swap applies to older gen 20rnd Pmags?

mjh30, can you provide a link to the post you're referencing? If you hadn't posted this I doubt I would've come across this info so thanks for posting it.