Have some Brownell 20 round metal magazines that are 6-8 years old. Use them in NRA/CMP High Power competition events.

Over the last couple of years I've had issues with just some of them which I dealt with by switching to new 20 round  MagPul magazines.

Yesterday, I used one of my metal magazines (just picked one out of the bunch I had brought along) and had issues with it.

Question... When I insert a magazine I aggressively get it into the mag well and slam it home to secure it.

Is it possible that over time I have deformed the feed lips due to my insertion method? By time I mean over a year/couple years if I  use them a couple times a month.

Do I  understand correctly that it really doesn't take much lip distortion to make the mag  a problem child.

When I  examine the lips I see nothing obvious. They are not DROPPED onto the ground during removal ( maybe 6 inches at the most and that is onto a shooting mat).

Thanks All

One way to be certain:

https://www.brownells.com/tools-cleaning/gun-tools/rifle-tools/ar-15m16-magazine-feed-lip-gauge/

And a resolution:

https://www.pacifictoolandgauge.com/AR-15-Magazine-Feed-Lip-Tool_p_114592.html

I used Brownells aluminum magazines for years during outlaw three gun competition for years.  Pretty abused, slammed into my M4 receiver,
dropped on the ground and always monopoded from prone.  I never had a problem. Never had to replace one.

That said aluminum magazines for the M sixteen series are disposable.  I used to take great pleasure in the Army by stomping on defective mags, taking out the spring and wrapping it around the body. And throwing it in the dumpster.

I have never distorted the feed lips on a thirty round mag doing that. Not really any different lip design than their twenty. I have even slammed fully loaded thirty round mags in hard enough the center piece on the follower put outward dents in the floorplate and never had a problem with feed lip damage. No problem from doing the same with a downloaded thirty round mag either.

Have seen mag lips being opened up and having problems after they were ripped out clearing feeding jams. I have a few old used GI twenty's that have feeding problems but they were used when I got them and are the Okay Colt open back style. Never really tried to see if they were too open or bent down.

magazines for any firearm are long term consumables.  

the only time I ever "repaired" one was when a new l1a1 mag was literally slicing a groove in brass during feeding - the feed lip on one side had never been deburred.  two swipes with a file to break the edge and it was gtg.  I was about to pitch it - then marked it and set aside.  then ten years later the damn things got expensive!   I should have bought dozens at $8 each when they were available.  

if any of my ar mags go bad, they will just get replaced.   the only expensive ones are the 6.8 spc dura mags, and those have been flawless so far.  the rest are pmags.

This
Mags are cheap especially 223/556

Once they start having issues I mark to test again then pitch once confirmed having issues