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FM Received - tough mag release on closed bolt


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Completed switch from AR-15 lower to Foxtrot Mike.  Upper uses Taccom 3-stage buffer and extreme bolt.  Rifle functions 100% with Glock 33 round mags and is incredibly soft shooting.  The only minor issue is the difficulty of releasing the mag on a closed bolt during "Unload and Show Clear".  I can easily circumvent by ejecting the chambered round and locking the bolt back, but I'd prefer to either a)find a fix or b)determine that there is no fix, it's just "life".  

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Hmm, I have a back-up PCC built with the FM Products Upper/Lower stuff and honestly recommend them (especially their Glock-mag lower) all the time due to their quality and tight tolerances (even against upper tier stuff like QC10 etc, incredibly good for the money really). One of the main reasons their lower is so nice IMO is that it holds the mags nice and high  and there’s almost no wiggle/play that you usually find in ones that don’t run so great... 

Mine too was a little sticky with newer OEM 33rd mags (like you, mostly on bolt-closed with rounds still in the mag), but after a bunch of reloads my mags wore in a bit and the issue disappeared... I think once things wear in you’ll appreciate the lack of mag play/wiggle, you might just want to do a bunch of dry-fire reload reps and speed up the process...

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ck,

Thanks for the response.  First thing I noticed is that the 33 rnd Glock mags are a bit snug going in, but that's a good thing versus SGM which are very sloppy in the magwell.  No doubt why they don't run and are, specifically, called out by FM as not suitable for their lower.  

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On 1/16/2020 at 12:23 PM, ck1 said:

Hmm, I have a back-up PCC built with the FM Products Upper/Lower stuff and honestly recommend them (especially their Glock-mag lower) all the time due to their quality and tight tolerances (even against upper tier stuff like QC10 etc, incredibly good for the money really). One of the main reasons their lower is so nice IMO is that it holds the mags nice and high  and there’s almost no wiggle/play that you usually find in ones that don’t run so great... 

Mine too was a little sticky with newer OEM 33rd mags (like you, mostly on bolt-closed with rounds still in the mag), but after a bunch of reloads my mags wore in a bit and the issue disappeared... I think once things wear in you’ll appreciate the lack of mag play/wiggle, you might just want to do a bunch of dry-fire reload reps and speed up the process...

Do you think that the mag is being held up so high that the lips are hitting the bolt? AND....whn you say worn it, do you think that the aluminum mag catch has worn into the magazine catch, lowering the feed lips. Huh? huh?.....well, at least that is the first thing I was wondering.

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20 hours ago, TRUBL said:

Do you think that the mag is being held up so high that the lips are hitting the bolt? AND....whn you say worn it, do you think that the aluminum mag catch has worn into the magazine catch, lowering the feed lips. Huh? huh?.....well, at least that is the first thing I was wondering.


Nah, it’s not the mag lips, it’s just the magwell being tight with newer OEM mags that bulge a bit when loaded... once the polymer mag bodies wear in a bit they become gtg.

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On 1/18/2020 at 11:49 AM, ck1 said:


Nah, it’s not the mag lips, it’s just the magwell being tight with newer OEM mags that bulge a bit when loaded... once the polymer mag bodies wear in a bit they become gtg.

good to know!! We did just have that issue with a lower holding a magazine too high and hitting the bottom of the bolt......easy fix

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I did a quick check with 15 and 33 round Glock mags loaded and empty.  The mags are definitely not in contact with the bolt.  Yes, the mag release is easier when the mags are empty and the release is definitely stiffer with a loaded 33 round mag, but I think that is somewhat do to the weight of the mag dragging on the mag release interface.  Found an easy solution, simply re-position my index finger toward the rear edge of the release.  The additional leverage worked just fine with loaded 33 round mags.

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