Retiring my first Pmags

[Jesse H]

When we got issued Bushmasters back in '08 I went out and bought my first 3 PMags. The two aluminum mags that came with the Bushmaster were tossed in a closet and forgotten about. Over the years I've stocked up on more PMags and D&H mags than I have a "need" for but I continued to use the same 3 PMags for duty and training, then a couple years ago I've only set them aside just for training, and they've been flawless. I've got new PMags loaded in my kit, but I always trained with the oldies. They were flawless with the Bushmaster, a DPMS which I promptly sold when I learned more about the platform (although the lower was very snug), my 6920 and now my current BCM that I use for work.

When the stamp was finally approved for the Saker K I was expecting issues with the 11.5" BCM upper and H1 buffer. Unsuppressed no issues, but with the can the bolt would fail to lock back on the last round. I just chalked it up to being overgassed due to the symptoms and with brass ejecting about 2 o'clock. So I ordered an H2 from BCM.

Same deal with the H2. Runs 100% unsuppressed but won't lock back on an empty mag. Same issue with all 3 Pmags so I ordered an H3. H3 arrived and I packed up for the range today, but for some reason I thought about grabbing those two aluminum mags that I was issued. I probably didn't grab a brand new Pmag or D&H mag because those guys were all boxed up in their packaging.

I loaded one round in each mag and the first two mags I tried were the aluminum ones. Locked back when empty. The third mag was a Pmag and it locked back as well. The remaining two Pmags didn't lock back. I went back and tried this several more times and the aluminum mags were 100% and the Pmags were about 50% in locking back.

I'll need to go back to the range again with new Pmags to confirm, but I'm willing to bet if they're locking back with these no name aluminum mags new Pmags should no longer be an issue with my BCM 11.5" and Saker K. I suppose I could continue to use the PMags for training for the unsuppressed guns, or maybe replace the springs and see if they improve.

I found this thread and found it interesting and possibly related as these old Pmags have the old style followers
https://www.m4carbine.net/showthread.php?101687-Suppressed-only-bolt-lock-malfunction-Ideas-Resolved&highlight=

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[markm]

You need an H3 at a minimum. Failures to lock back shouldn't be happening on even old mags. H2 is what you would run with no can on an 11.5.

[jstalford]

This exact thing happens with my 11.5 and saker 762. Already running a5h4 so can't go any heavier.

The gas port on mine is .069 so smaller than most 11.5. After messing with a bunch of shit and it still happens the only common variable is gen2 pmags.

Gen3, D&H/NHMTG, lancer all lock back fine regardless of ammo.

ETA, my gen2 less than a year old and low round count.


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[Jesse H]

All my new Pmags I've got squirreled away are gen 2, so we shall see next week when I get a chance. This is with an H3, and although I don't know the port size for BCM 11.5" I do recall remembering they were good for suppressed.

[jstalford]

I think BCM is .076, so bigger. I have the same problem with my BCM 11.5 barreled upper.


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[TommyG]

You need an H3 at a minimum. Failures to lock back shouldn't be happening on even old mags. H2 is what you would run with no can on an 11.5.

My DD 11.5 is working with my Sandman S and and an H buffer in a BCM factory lower. Should I be jumping up to an H3 to ward off the boogieman in the future?

[nml]

Sandman has lower backpressure than most especially on 5.56. Still I'd run some low powered stuff unsuppressed to get an idea of what buffers run. My DD midlength locks back H3 unsuppressed for example.

[Singlestack Wonder]

You need an H3 at a minimum. Failures to lock back shouldn't be happening on even old mags. H2 is what you would run with no can on an 11.5.

+1 on this. I have an 11.5" BCM and run a Saker 5.56 with an H3 buffer. Never had an issue with anything. All of my PMAGS lock the bolt open on empty.

[TommyG]

Thanks. I don't want to go shopping for a problem where one does not exist.

[jackblack73]

With mags that old, that sound like they are well used, wouldn't they benefit from new springs?

[vectorsc]

Whew - 8 years isn't bad right?

[sevenhelmet]

8 years is just a period of time. Any estimate of how many rounds you have through those PMAGs?

[Jesse H]

Just a wild ass guess, but roughly 10-12K rounds and that would be split between 3 mags.

Went to the range this morning with the following mags, and still using an H3 buffer, Silencer Saker K, factory BCM 11.5 upper and BCG:

5 duty mags
4 2013 Gen 2 FDE
1 2009 Gen 1 black

For most of their life they've been loaded with 30 rounds of duty ammo and lived in my plate carrier. No issues at all, they all locked back the bolt on empty. I tried loading one round each, and also loaded several rounds each and shot quickly. After each mag did so without issue I was confident with these.

the same 3 old Pmags from 2008
These are the guys that have seen a combined ~10-12K rounds and have been used for training. These mags all say patent pending on them and have been great unsuppressed. Each mag would fail to lock the bolt back with a single round. These were the first ones I shot today so once they failed on the first try I set them to the side and spent the rest of the morning testing the new mags.

additional original 2008 Pmag that was sitting around unused
Failed to lock back on empty.

gen 2 that I had laying around that's got light use but still looks fresh
I really thought this one would work without issue but it failed to lock back on empty. For kicks I replaced the follower, spring and baseplate with one of the FDE ones that were good and it would lock back on empty. In hindsight I should have also replaced the spring by itself, then the follower.

3 brand new gen 2 Pmags still in the wrapper, build date 2013
No issues. I spent the rest of the day loading only a handful of rounds in each mag and working on transitions and mag changes so I could get lots of reps in with going empty.

What I noted were the mags that caused me issues had a nick in the top of the follower. I'm guessing this is a result of the malfunction and not the cause? As in, the bolt riding over the empty mag is causing the nick. Also, the bolt catch also developed a slight nick, which can be lightly felt with my fingernail. I circled the picture in red. For comparison I looked at my Colt and it appears normal.

So I'm sure the root cause is still suppressor resulting in a faster bolt speed. With the H3 it's still ejecting forward of 3 o'clock. Next time I'm going to independently replace the spring of the bad mags with good ones. Then the follower to see if I can pinpoint what component of the old Pmags are preventing lock-back on empty. I also should've tried some duty ammo which is likely hotter (Gold Dots) than our practice ammo (Remington UMC), just to confirm things would work ok with the last round.

[sevenhelmet]

That actually makes me wonder if Magpul changed to a stiffer spring sometime between 2008 and 2013 (would be the first I'd heard of it). But even your oldest mag shouldn't be "worn out". I'm still thinking gun issue. Could you try removing the suppressor to see if the same mags would lock back without it?

[jstalford]

My mags are from 2015 and have the same issue. They do lock back unsuppressed.


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[Jesse H]

Yes they all lock back on empty when unsuppressed.

[Firefly]

Still use some first run pmags. They still work. Even some of my thermolds now and then.

[sevenhelmet]

So, if I'm reading this thread correctly, this seems like more of an issue with running a suppressor than an issue with Pmags, or mags in general.

[Jesse H]

So, if I'm reading this thread correctly, this seems like more of an issue with running a suppressor than an issue with Pmags, or mags in general.

Yes and no.

All of the magazines work just fine on my 6920. Most of my Pmags work fine on my suppressed 11.5" BCM. So far every aluminum mag also works fine with my suppressed 11.5" BCM.

I forgot to mention the mags that didn't work with my BCM did work on my buddy's gun which uses the same BCM upper. He has a different rail and Surefire Socom Mini can.

[jstalford]

Mini can prolly creates less issues since less backpressure.


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[Defaultmp3]

Already running a5h4 so can't go any heavier.You sure can: http://heavybuffers.com/vltor.html

[jstalford]

Eh, I remember hearing something I didn't like about those buffers so I never went that route.

I'll never find the reference again so I can't tell you what it was, but it's not a big enough issue for me to swap. I have triple digits of mags and like 10 are gen2 pmags. It's just annoying.

I'm also running a small port 11.5 barrel so I don't think heavier is necessary to fix a mag issue


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[sevenhelmet]

I'd be curious to note how many guys with suppressed SBRs are having this issue.

Could it be the that the Pmags have a slightly lower spring force due to them being slightly longer than USGI mags? We geek out on measurements a lot- has anyone ever checked their mags with a force gauge?