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My empty 3rd Gen magazines have been a little difficult to remove from my CMMG lower and have always needed a little tug to extract. This is ok when shooting from a bench but not very useful when shooting any kind of tactical shoot where quick mag changes are key and where the mags need to drop free under their own weight while the free hand is grabbing a new mag so I went about finding the sticking point and after a little investigation I think I've succeeded.
The magazines were tight to insert and tight to remove. So I started with the upper nubs on the side of one of my mags, removing a very small amount of material using 600 grade wet and dry. No noticeable difference.
Next I tried the rear of the mag on the upper part of the rear hump, again no noticeable difference.
So all that was left was the front of the magazine. I noticed witness marks on the inside of the magwell so I started on the front of the magazine between the nubs with 240 grade wet and dry paper and finished off with 600 grade wet and dry.
That has made a massive difference and now the mags drop freely when empty and there is also a very noticeable difference when inserting a loaded mag.
I've added a picture to help show the witness marks. you'll need to keep rubbing until these marks are no longer visible.
Hope this helps the guys with the new CMMG magazines as I know it has been a problem for some. Let me know if this works for any of you.

Thanks. This can happen will most moulded magazines and often depends on the lower receiver dimensions, some rifles are ok and some not so. Taking your time and removing as little material as possible is the key.

Have you had it on the range since doing the modifications and does it still load as reliably as before? Is there any movement front to back and if so does it still load when the magazine is in those positions?

DM

Dangermouse wrote:Have you had it on the range since doing the modifications and does it still load as reliably as before? Is there any movement front to back and if so does it still load when the magazine is in those positions?

DM

Yeah, used it today and its perfect...they are so much easier to remove...there is no forward or backward movement, as someone mentioned before just remove a very small amount...mag changes are now super slick...

I gave up. This is CMMGs 3rd gen mag and they've all been useless. They seem completely unable to make a mag that consistently fits their own firearms, that can load to full capacity and that always activates the BHOA. It's actually quite embarrassing. I switched to the S&W with the Better Mag and couldn't be happier. They do exactly what you'd hope for and to be fair to S&W they've been doing this for over 5-yrs ! It must be rocket science.

as JMH says, its an issue with moulded mags, also, not all AR's are made to spec, you can take a mag and try it in 3 different magwells, they all fit differently.
even the big boys (magpul) have issues with this