Getting ready for my next Run'n'Gun event. I decided to sort through my PMAGS and find the ones that don't seem to seat easily on a closed bolt. Seems like every event I've run in I'll encounter a mag that I just can't seat and it screws my time on a stage.
The culprit mags show a unique failure where the second round in the magazine sticks up:
When this happens the 2 rounds lock on each other and it takes an enormous amount of force to insert the mag. Pushing the tip of the second round down to it's normal position fixes the issue. I can induce this failure by aggressively slapping the bottom and sides of the mag, or by dropping it on dirt/carpet. Not good for someone running and doing obstacles.
Taking a closer look I realized some of my mags just flat out wouldn't allow this to happen. There appears to be a geometry change. Magpul added a 2nd "guide" rib just in front of the feed lip. See below a magazine with the added rib and one without:
There is also an external marking which I believe is the version number. I checked all of my M3 PMAGS and they were marked either "20" or "22". Version 20 exhibits the failure, 22 does not. My M2 PMAGS were version 10 and have the same failure.
Of all my M3 PMAGS I've got a 50/50 mix of 20's and 22's. I'll be keeping the 20s for practice and to sell off during the next scare.
If you're inspecting a new in wrapper magazine you can see the number without opening the package.
I haven't purchased any PMAGS in a while so I'm not sure if 22 is the most current version or not. I'd expect any number greater than 22 to include the same fix.