A few weeks ago I was shooting my M16A1 on Rock & Roll.  Because I had forgotten to bring along my second upper I had to wait very often for the barrels to cool down.  Shoot one 30 round magazine and then wait several minutes.  There was no feeding problems at all.

And then, right out of the blue the floor plate failed on one magazine.  It went in normally, one round was shot off, and the floor plate completely failed.  Down came the remaining 29 rounds, spring and follower.  After checking to see that the chamber was empty I put the rifle down I collected the rounds and put them into my Range Bag.  The magazine itself was collected and put back into the magazine carrier.
Something like this had never happened to me in all my years of shooting.  So when this happened three more times I think you can understand me getting a terminal case of “WTF, Over??”
One floor plate went missing.  Which is about the most anticlimactic thing I can say about the whole thing.

And then to top things off many of the remaining magazines didn’t want to catch when they were inserted.  When I used them I had one hand on the pistol grip and one hand holding the bottom of the magazine.  And almost needless to say; when those magazines were empty I needed to use the magazine release button.

Later, back at home when I put those magazines back together one magazine seemed wider than the floor plate that seemed to go with it.  It seemed like it was swollen from something or another.  I didn’t bother to put that magazine back together.

Some of these magazines aren’t that old; two of the failures were purchased in Sept 2004 as part of an AWB expiration Group Buy; I have older shoes.

A week before I went each magazine was loaded to 25 rounds each.  And a few days later they were all topped off.  Several months ago I had left 12 of these fully loaded magazines in their magazine carrier in the trunk of my for several weeks before using them.  As I had no problems with the magazines then, so why should I suddenly have problems with them now?

Either next month or in June I’ll be buying replacements for the magazines that failed.
Why the floor plates had to suddenly fail on me is way beyond me.  The 13th was several days in the past when this happened.  That’s the only thing that I can think of that makes more than no sense at all.

You had three mags fail in the same way?  If you had three, it sounds like something else is going on besides bad mags.  Did you look at fired cases?  Any case ruptures, blown primers or other sign of problems with them?

It almost sounds to me like one-too-many rounds were put into the magazines and they were damaged by the force of getting the mags to lock up.

Based on the info provided, I'm guessing the mags were not heat-treated.
Would be interesting to know the manufacturer of these mags....?

Hotgun

Do you often say "over" to yourself?

You must have been in the Military too long, dude!

Make and Model of the mags?

We need pics as well. Sounds like some of the pressure from the chamber was bleeding into your rifle. However, that would mean a cracked bolt or worse. Make sure you check your gun before shooting it again!

Quoted: Make and Model of the mags?

+1 over!

Quoted: Make and Model of the mags? We need pics as well. Sounds like some of the pressure from the chamber was bleeding into your rifle. However, that would mean a cracked bolt or worse. Make sure you check your gun before shooting it again!

+1