View Full Version : 9 mm AR Mag Catch Problems

06-02-2009, 7:16 AM
I am building up a 9 mm lower while I wait not so patiently for my 9 mm upper to arrive. I got the lower put together last night and I have a problem with the magazine catch. I am using a Rock River conversion block in a CMMG lower with RRA 10/25 plastic mags and a bullet button. After completing the build, I inserted an empty 10/25 mag in the magwell and it went in fine, but the mag catch will not hold it in place. It stays ok, but the slightest tap to the magazine, and it falls out. When I filled the magazine, it became slightly fatter due to the rounds and spring pressure, and stayed put until the mag was depleated down to 1 or 2 rounds, then it could be easily dislodged (read removed without a tool). It looks like the mag catch is not fully engaging the hole in the magazine. Anyone else have this problem, and know a solution? I thought about bending the mag catch so that more of it engages the hole in the mag, or making a larger step in the mag catch, but I would like to hear other ideas. Maybe the plastic mags are just crap?


06-02-2009, 7:24 AM
I experienced this same exact problem. What was happening was the mag catch was touching the mag catch cutout on the mag block and rubbing against it. This caused it not to sit all the way causing the loose dropping mags. Take the mag block out and give it an ever so slightly touchup with a very fine metal file and then re-seat it. Make sure it sits at a depth where the mag catch does not touch the mag block at all. Mine now works like a charm and mags have a solid reliable lockup.

06-02-2009, 11:07 AM
I had the same problem with a Lauer Lower. Couldn't get a mag to lockup with a RRA Conversion Block. The mag would hold up until I put some pressure on it. I tried EVERYTHING to make the mag to lockup with several different kind of CA Bullet buttons and mag release catches.

I decided to switch the 9mm setup to a DoubleStar lower and it worked great.
The mag locked up great with the conversion without any problems.

I read somewhere on ARF that the magazine wall thickness on some lowers are slightly different. Thus, for my case the Lauer magazine wall was thicker than the Doublestar. Which didn't allow the magazine release catch to engage both the conversion block and mag at the same time.