Question: I finished my first AR build and the only problem I have found is with the magazine catch. It is sort of “sticky”.

Background:  I used a New Frontier polymer lower receiver.

I have polished the flat sides of the mag release latch (where it would rub on the receiver) with 600 grit emery paper.

I used moly grease (sparingly) on the spring and threaded post part of the receiver catch assembly.

I tried varying the number of turns on the magazine release when threading on the button on the other side.
Nothing works so far. It still drags somewhere.

I have a collection of magazines, original Colt 20-round, Thermold 30-round, and Magpul Gen II and Gen III 30-round. The latch will engage on everything except the Magpul Gen III. Also, I compared the amount of “wiggle room” after the magazines were in the receiver between my new rifle and an older Colt I have. After the magazine catch engages, there is more up-and-down play on the Colt than on the new rifle.

So, any suggestions on 1) what to do about the “sticky” magazine release and 2) what can I do to get it to work with all magazines?


For starters, know that the gun is not in front of me, so troubleshooting is truly going to be based on knowledge and not what I can see or feel.

My first reaction is to think that you’ve got a warped mag catch area on your lower. I’m not sure when you received the lower, but the ones made during the “gun panic” had these exact same issues. Whether the lower was still warm from being molded and became warped, or whether it had been allowed to cool and then warped.

What you may want to do is see exactly where it’s catching. It’ll probably be predominantly in the area where the mag latch goes into the mag well.

You can either trim it with an exacto knife, or take your time with some 400 grit sandpaper to open up that area JUST A LITTLE BIT (you don’t need a lot).

This should allow the mag catch to go in a little deeper to catch the Gen 3s. If not, it may be that your mag latch is defective (this is highly unlikely, but again, if you purchased during the “panic”, many manufacturers were solely concerned with filling orders and less with quality control).

Of course, you can always ship the firearm here and we can get it done for you. We’re always happy to help!

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