P-Mag Follower and Bolt Catch Engagement *Issue Resolved!*

AR/M4 AR Technical Discussion
1

I was fooling around with my lower today when I noticed the rear of the Pmag follower was on the very edge of the bolt catch in my lower. With a bit of forward wobble, the follower slips upward and the bolt catch is now pinned against the back of the follower. When this happened the mag had to be pulled out by force, as opposed to dropping free. I’m very troubled by this and am concerned about the reliability of my new Pmags.

I checked the bolt catch engagement with my USGI and HK mags. Both good. The bolt catch gets good engagement over the back of the follower on each. But with forward tilting on a USGI green follower, the same error occurs, however this forward cant is far greater than anything I expect to ever happen in real use, whereas the error in the Pmag is triggered by mere wobble, perhaps 1mm at most.

Seeing this, I decided to test the magizine with the upper to see if it made a difference. It did. The tension on the bolt catch by the BCG helps keep the bolt catch firmly engaged over the rear of the follower of the Pmag. However, when using the CH to keep the BCG to the rear, the follower can slip past the bolt catch when slammed into the magwell or when jarred or shaken significantly after insertion.

I performed the same series of tests on another Pmag with similar results, this leads me to believe it is common in Pmags, or there is something wrong with my lower.

Whether or not this is a legitmate problem causing error in real use, I’m not sure. I will test with another lower to see if it has similar problems to confirm if this is a mag follower issue or something unique to this lower.

ETA: Just tested the second lower. It too appears to have the same problem. I’d like to clarify that this is not a bash against the Pmag or Magpul, I have tons of ladder and XT panels, a CTR stock, MIAD grips, and now Pmags. I’ve been happy with every single product. I’m just raising a concern and asking about what ,if any, fix is recommended or if it is even a significant issue at all. For what its worth, I have no plans to go back to using USGI mags.

ETA2: I’d appreciate it if anyone else who is using Pmags or has had great experience with PMags could try this test and hopefully confirm my feelings that this is an issue that while possible, never manifests itself it real use.

2

Here are pics-

This is of the hammer forward applying forward pressure to the bolt catch, note the positive engagement of thefollower.

Here it with no forward pressure, there is less engagement of the follower.

And finally, after nearly any forward pressure to the follower causing it to wiggle forward…

The bolt catch has slipped the follower and is now pinned against it.

3

I would suspect the magwells on your lowers are on the larger side of the tolerance range, or there is an excessive amount of play in the area your bolt catch its into in the receiver. Just checked in two of mine, a Spikes and a GTS/Stag, and there is virtually zero front to back movement of the magazine, and zero movement of the bolt catch itself. No where near enough movement anywhere to allow the bolt catch to drop behind the follower as it is doing on yours. I would personally suspect your bolt catch area in the receiver. It appears to be on the large side, thus allowing the catch itself to move as is evident by the hammer pushing it forward in the proper place, but allowing it to move back when the hammer is cocked. Combined with whatever movement you may have from the mag well, it may be enough between the two to add up and cause your issue.

4

In fact, after looking at your pics closer, you can see in the pic with the hammer down, that the bolt catch is pressed against the front of its channel with a small gap at the rear. In the 2nd pic with the hammer cocked, you can see that same gap is now at the front with the bolt catch pressed to the back of the channel. That combined with maybe a slightly large magwell, you could be seeing enough tolerance stacking to cause the problem.

5

Thanks, both lowers are BM, as are the parts in them. I’ve always been thankful of my somewhat loose magwells, but I see where its causing some issues here. I’ve shot all 8 of my P mags through 30 rounds each and no issues so far, I’ll do some more shooting with them tomorrow. I’ll update this thread with the results, but I feel like this is a non issue, with the bolt catch always under pressure from the BCG when the mag is empty, and this “flaw” being meaningless until the mag is empty, I don’t see where this is going to cause me problems in actual use. Time will tell though.

6

Try tightening the mag catch an extra turn.

7

Just did this, no difference. Mag still wobbles the same and the error still remains.

Are there any extended tip Bolt Catch parts out there?:confused:

8

I just checked and my BM lower does the same.

If it is any consolation, It has caused no issues.

The Colt does it too.

9

Mabey Magpul will sell one!

Seriously, don’t worry!

10

I agree its a tad crazy I’m worried now that I noticed it may cause problems, when in actuality they’ve done fine so far, and prolly will throughout their service life, the same as if I’d never seen it at all.:smiley:

11

What part of the firing cycle, the reloading process or even normal administrative handling do you think would replicate the follower being pushed that radically rearward?

12

Exactly. Thats the thing, I doubt it interferes with normal function at all, so I’m probably just being paranoid. Time will tell, so far no problems with any of my Pmags and I doubt I’ll ever get any problems with them (except for not having enough on hand:D )

13

It’s not often I say this, but you’re thinking too much dude :wink:

14

YUP
Never had or seen that with any PMAGS (and I’ve seen a ‘few’)

15

…personally, I try to not screw with stuff that ain’t broke……but, that’s just me…ymmv

16

Well, just got back from the range, everything functioned perfectly, as usual. Pmags worked 100% in both AR’s, with a variety of ammo. No sense in losing sleep over it, as the Magpul guys (with inspiration from Dr. Stangelove) say:


I’ve come to stop worrying and love the polymer magazine!

17

i tried to get my one pmag to do the same thing but cant. although it it brand new there is less then 1/16 of an inch of the bolt catch resting on the follower.

18

I don’t think this problem can be replicated in actual use.

Take all of the P-Mags you own and load 3 rounds in them. Then, as quickly as possible, fire and reload mag after mag. Repeat until you are satisfied you will not have a problem.

19

Update:

This issue is becoming increasingly common in administrative handling. The follower ‘pops’ up past the bolt catch now as long as two requirements are met:

1- The mag is jarred (inserted firmly, or pushed rearward)
2- The bolt catch is not under tension from the bolt carrier

I’m becoming very uncertain about my decision to transition to Pmags, the next available range trip I will test each of the 8 I have repeatedly to see if this defect is present in live firings (I will test the mags when using magwell grip and using the mag as a monopod as these seem to be the positions it is most likely to occur in). I wish the PMags were capable of a longer follower, but the thickness of the mag body seems to prevent this. I can see no quickfix that Magpul could implement to the existing Pmags to stop this.

At this point, I am considering switching back to USGI mags. I am aware that the USGI mags are plagued with problems, although I have never personally experienced any with my own, but I cannot use magazines that cause major functional failures. This will all depend on what happens when I test the mags. I’d very much like to continue to use Pmags, after all I spent $114 on them and want to see that they are reliable.

NOTE I HAVE NOT YET DONE CONCLUSIVE TESTING ON THIS ISSUE! ALL TIMES I HAVE USED A PMAG LOADED WITH AMMO I HAVE HAD 0 MALFUNCTIONS! THIS CONCERN HAS ONLY BEEN SEEN IN HANDLING OF THE UNLOADED RIFLE AND MAGAZINES!

It is not my intent to bash Magpul or imply that all Pmags are flawed, although at this point, my specific rifle and magazine combination may very well be.

20

How many of the USGI did you originally have? What is the date code on the PMAG tubes?