Had my first one this month.  Old plastic mag I've probably inserted... gosh hundreds of times.   Basically, with insertion while the bolt is locked back, the mag went in past the stop, and the bolt release couldn't work.  Fix was easy enough, just tug the bottom of the mag.  Not a huge deal, mag is functional.

But I'm curious, is this an unavoidable flaw of aging plastic magazines?  Are metal mags immune to this possibility?   PMag's latest designs apparently have an overinsertion block now (my example is an early generation 20 round PMag).  Is this something Lancer and ETS mags are at risk from, just like the early generation Pmag?  Or has polymer chemistry evolved to be different/stronger?

Just curious - it wasn't a big deal.

Seems to me that metal mags would be more prone to overinsertion. it also seems that a good mag catch would stop most overinsertions.

Well... sure I could see that.  but really if you take a grown man and he slams a magazine into the well with significant vigor, it's kind of asking a lot for that little bump to stop it.  To be honest, now that I think about it, I'm kind of impressed it works as well as it does, as often as it does.

A couple generic internet photos:





But I see what you're saying.  It sort of seems like the metal should hold up better - I guess.  Then.... well take a look at the mag on the left, and tell me that doesn't look like some kind of wear.  Anything that diminishes that surface from being perfectly square, is going to be susceptible to letting something slip when you slam the Hell out of a Mag.  So I can see Magpul's response.

My PMag has gotten ever slightly worn there at the insertion stop bump, which I suppose didn't help.  Most of the time it would never be the issue, but a real heavy slam, and wups - over-insertion.  I could complain about the PMag, but then, maybe a GI of similar age and use would have done the same.  And that $18 PMag has outlasted a $300 Barrel, and it's about to outlast another barrel and a bolt.  That's.... pretty darned good!

I've done some hard slap ins with plastic mags and never over inserted any.  Wife sez she doesn't worry about it either.

I have an early E-mag I over inserted. Still works but stop is damaged.