Was shooting my suppressed 9mm AR build today. 8" TROS USA barrel, CMMG ramped BCG, and Metalform PSA mags. Slash's heavy buffer. Ammo used was Federal AE 147 grain.

When it got down to the last few rounds in each mag the rounds would double feed or pop out of the mag and float around the chamber. I've always heard Metalform makes really good mags and I have about 30 of them... all seem to have this problem.

Another strange thing I had loaded up 10 mags, threw them in a case and drove the Jeep out to my shooting spot. Road was gravel and pretty bumpy. When I opened the case I saw that each mag had a round or two pop out of it just from driving.   All of these mags were purchased around the same time. Possible weak batch of magazine springs?

I use a 5 inch tros, cmmg bolt and the psa mags in mine, and don't have any issues like that at all. My guess is something's off with the magazines.

My advice...take a few mags apart, use some  alcohol-type cleaner on a rag and pull the rags through the body to clean out anything.
Wipe follower off, and wipe the spring.
Inspect the follower for any rough edges, smooth out those areas.

Re-assemble the mags, and go try them out to see if there is an improvement.


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not metalform, so may not be your issue.
I found that using a spikes mag block and the asc mags that the follower would hang up on the feed ramp.
made the last couple of rounds not work right.

you might take a look with the upper off.
I just pushed off the top rounds and saw that it hung up when there were like 2 left in the mag. depending on how I held the mag, sometimes it would slip off, but there was no tension on the last 2 rounds.