Problem with a new BCM lower

[BufordTJustice]

It seems like this could have been avoided if Magpul had done more extensive testing with other lower receivers. I can't help but wonder if they focused on testing with Colt and FN lowers and didn't pay as much attention to the BCMs of the world.

Here's some perspective:

As much as I like, advocate, and use BCM products, who should be catering to whom? Magpul, whose gen 3 pmag works with ALL receivers that conform to the TDP, or BCM, whose receivers deviate from the TDP in this particular (non critical) dimension?

[POB]

I am probably way off base here but isn't the area of the BCM magwell in question the lower rear part nearest the trigger guard? or the front? Isn't this the part of the forging process? and where does BCM get their lowers? I thought that was top secret. LOL You would think they would all affect the same forgings unless there is machining that BCM left out. Don't mind me I'm drinking.

[Wake27]

I am probably way off base here but isn't the area of the BCM magwell in question the lower rear part nearest the trigger guard? or the front? Isn't this the part of the forging process? and where does BCM get their lowers? I thought that was top secret. LOL You would think they would all affect the same forgings unless there is machining that BCM left out. Don't mind me I'm drinking.

It's the part nearest the trigger guard. I'm sure it's because BCM has a small flare to their mag well which is always a nice feature.


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[P2000]

Weirder still: my entire agency (1200 LMT patrol carbines and counting) uses gen 3 pmags exclusively without issue. Our 1500-or-so colt 1033 program 20" M16A1's also functioned without issue using the gen 2 & 3 pmags, before we returned them to Uncle Sam.

Logic dictates that some other variable is at play.

This thread has been quite interesting and confusing. I've changed my mind on who to blame for this issue 3 times.

Part of the beauty of the AR-15 is it's modular design. Without placing any blame on the mags, the mag catches, trigger guards, or the lowers, in an ideal world this type of issue shouldn't happen using properly dimensioned AR parts. I think this kind of thing should be respected to the fullest by any AR-15 manufacturer, but limited access to the TDP might make things squirrely.

So is Magpul basing their design off of the lowers from companies that have a tolerance which is within the TDP, but in this area much tighter tolerance than the generous amount allowed for in the TDP?

I assume Magpul does not have the TDP, and neither does LMT? Is this a consequence of reverse-engineering?

I give up. Goodnight.

[DreadPirateMoyer]

Out of curiosity and to see if my lowers had the same issue, I pulled 10 M3 PMAGs and all of my lowers and went to town on seeing if they'd work with a closed bolt. Lowers tested were BCM, DD, Colt, and KAC.

The PMAGs were fine in all lowers, BUT all of my BCM lowers (multiples) had much less space between the over-insertion tab and the rear of the magwell. All of the other lowers from other companies had noticeable space between the tab and magwell/trigger guard; it was visible and one could see through the gap. All of the BCM lowers were tight and had no visible space in the gap, though still worked.

It obviously would require more thorough and representative testing, but in my small experiment, it seems the problem is on BCM's end, not Magpul's. Even as a rabid BCM fanboy, I too wonder how this problem would've been confronted in this thread had the brand been DPMS or Spikes or some other trash. I doubt Magpul would be getting any heat here.

[RazorBurn]

Out of curiosity and to see if my lowers had the same issue, I pulled 10 M3 PMAGs and all of my lowers and went to town on seeing if they'd work with a closed bolt. Lowers tested were BCM, DD, Colt, and KAC.

The PMAGs were fine in all lowers, BUT all of my BCM lowers (multiples) had much less space between the over-insertion tab and the rear of the magwell. All of the other lowers from other companies had noticeable space between the tab and magwell/trigger guard; it was visible and one could see through the gap. All of the BCM lowers were tight and had no visible space in the gap, though still worked.

It obviously would require more thorough and representative testing, but in my small experiment, it seems the problem is on BCM's end, not Magpul's. Even as a rabid BCM fanboy, I too wonder how this problem would've been confronted in this thread had the brand been DPMS or Spikes or some other trash. I doubt Magpul would be getting any heat here.

I've been following this thread since day one, and your closing thoughts are the same as mine...

I also understand the OP's dilemma in that he has to have a lower that will accept whatever magazine that could be handed to him in the heat of the moment. I myself wouldn't be satisfied either.

[Toecheese]

I would try a few other magazines, but yes, it really sounds like something is out of spec with this lower.You did the right thing by contacting BCM before addressing it on here. Hopefully some pros can nail down whats up.

Not sure why sending it back to BCM before posting about the issue is a big deal.....everyone knows BCM is legit and stands behind their product, so if the OP just wanted to start his own thread about a BCM lower being out of spec before contacting BCM, that's entirely his prerogative.

[lengthofpull]

Not sure why sending it back to BCM before posting about the issue is a big deal.....

Perhaps because it is a forum rule?

[Toecheese]

Perhaps because it is a forum rule?

So if the OP sent his lower back to BCM, and started a thread that said basically "issues with BCM lower, sending it back will keep everyone posted".......what code of ethics or rules is he breaking? I find it interesting how the overall consensus on these forums is to throw a blanket over everything in regards to gun companies, basically giving them a free pass regardless of if they are at fault or not. I guess when you rely on sponsorship just to stay afloat, it's important not to bite the hand that feeds, which is a shame because there is zero transparency and a complete conflict of interest.

[Jaysop]

So if the OP sent his lower back to BCM, and started a thread that said basically "issues with BCM lower, sending it back will keep everyone posted".......what code of ethics or rules is he breaking? I find it interesting how the overall consensus on these forums is to throw a blanket over everything in regards to gun companies, basically giving them a free pass regardless of if they are at fault or not. I guess when you rely on sponsorship just to stay afloat, it's important not to bite the hand that feeds, which is a shame because there is zero transparency and a complete conflict of interest.

No its so whiney people don't start bashing companies before the situation can even be adressed. Give the manufacturer a chance to fix it or tell someone they're using it wrong first. The other site is full of people bitching about shit like that. Maybe that's where you would be happier.