BCM Lower not compatible with PMAG Gen3

[Biggy]

I try all my rifles or lowers for Gen 3 comparability before I buy them or do the transfer on an online lower purchase .

[Wake27]

One thing we should note is that BCM has a more flared magwell than Colt, which most people would agree is an upgrade to milspec and you really can’t say the Colt is of higher quality for that reason.

However, I don’t see why BCM can’t make a slight adjustment to that area of the lower while still maintaining the flare. Magpul had more of a valid reason for the tab than BCM has for them mags not fitting. This issue won’t go away, they’re just doing themselves a disservice. I’m a huge BCM fanboy and will continue to buy their products but no more lowers.


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[ace4059]

One thing we should note is that BCM has a more flared magwell than Colt, which most people would agree is an upgrade to milspec and you really can’t say the Colt is of higher quality for that reason.

However, I don’t see why BCM can’t make a slight adjustment to that area of the lower while still maintaining the flare. Magpul had more of a valid reason for the tab than BCM has for them mags not fitting. This issue won’t go away, they’re just doing themselves a disservice. I’m a huge BCM fanboy and will continue to buy their products but no more lowers.


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The reason it is “more flared” is because there is more material hanging down to flare. If it was the same as the colt then the flare would be the same.

I think if you buy a non blem lower it should work with a gen3 pmag. Pmag is an industrial standard. Hell, they maybe more popular than aluminum mags. Basically if we as a forum stop accepting BCM’s excuses then they would have to change it. I’m a bcm fanboy but if another company had this problem, especially ones m4 looked down on, this site would be bashing the shit out of that company. Let’s get real people.

Due to the thread from ‘15 I haven’t purchased any other BCM lowers. They have lost several sells from me due to their response. But now I several battle arms, and colt lowers that work perfectly with pmags. CS makes or breaks a company.

[Todd.K]

Pmag is an industrial standard.

No, M-LOK is a standard. With a print.

Lobby MAGPUL to put out an actual dimension that is compatible, then ask manufacturers to add that dimension. This is really quite simple.

[mack7.62]

Point to an issue rifle that will not take a Gen 3 PMAG, COLT, FN, HK® 416 and MR556A1, M27 IAR, British SA-80, and even the FN® SCAR™ MK 16/16S all work with them. For BCM to make the claim that it is a non mil spec magazine problem and not their problem is ludicrous when they work in all those issued rifles. They have a NSN, is the only magazine the USMC will take to war, approved issue for Army and Air Force yet BCM is OK with building non compatible lowers. I don't know why they want to take a stand on this when it is not that hard to fix but so be it, I will now lump BCM lowers in with all the older silly Colt lowers with non standard pins, sear blocks etc and will not own one.
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[ace4059]

To me that is pretty much an industrial standard if it works with just about all other lowers and several different Firearms.

[usmcvet]

Point to an issue rifle that will not take a Gen 3 PMAG, COLT, FN, HK 416 and MR556A1, M27 IAR, British SA-80, and even the FN SCAR MK 16/16S all work with them. For BCM to make the claim that it is a non mil spec magazine problem and not their problem is ludicrous when they work in all those issued rifles. They have a NSN, is the only magazine the USMC will take to war, approved issue for Army and Air Force yet BCM is OK with building non compatible lowers. I don't know why they want to take a stand on this when it is not that hard to fix but so be it, I will now lump BCM lowers in with all the older silly Colt lowers with non standard pins, sear blocks etc and will not own one.
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I have two BCM SBR’s. I have no freaking idea what generation my PMags are. How do I tell? Every mag, including PMags! I’ve used have worked.


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[mack7.62]

The Gen 3's have the dot matrix pattern for numbering and the over insertion tab at the rear.

[Wake27]

I have two BCM SBR’s. I have no freaking idea what generation my PMags are. How do I tell? Every mag, including PMags! I’ve used have worked.


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It’s definitely not an issue with all BCM lowers. The one I have works fine with every M3 PMAG I’ve tried so far.

There are plenty of other flared lowers that the mags will work with too.


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[Bolverk93]

The issue isn't with the design. It's with the tolerances that BCM considers acceptable.

This definitely doesn't affect all BCM lowers.

Does anyone know what mags their complete rifles come with?