BCM Lower not compatible with PMAG Gen3

[Bolverk93]

In case anyone else wasn't aware of this. I wasn't.

Apparently not all BCM lowers are compatible with M3 PMAGs. I just completed a build using a BCM lower. When I took it to the Range I realized that I could not fully seat any of the Gen3 PMAGs I brought. The issue is that this version of the PMAG has a tab on the spine of the mag to prevent over insertion. On this lower that tab prevents the mag from being fully inserted.

I e-mailed BCM about it, and their response was that this sometimes happens with their lowers, and I should only use mil-spec mags with their "mil-spec" lowers. They claimed that there are no tight controls on this area of the lower.

The issue that I take with their answer is that M3 PMAGs are mil-spec in that they have been issued an NSN (1005-01-615-5169) and are approved by the Army and the Marine Corps. In fact the mags I was using were issued to me, and are what all my teammates use in our Colt M4s with no issue. I have also never had issue using these mags with my DD rifles or guns built on Spike's lowers.

Live and learn. I'll stick to Colt and Daniel Defense, or even Spikes lowers when I want to build something.

[mig1nc]

I have a Noveske with the same problem.

But I have a cheapo range toy poly lower that doesn't... Go figure.

I am surprised with the BCM response though.

The M3 PMAGs have problems with lots of different weapons. But they seem to be great for their intended role.

Sent from my Pixel 2 using Tapatalk

[Renegade]

The issue that I take with their answer is that M3 PMAGs are mil-spec in that they have been issued an NSN (1005-01-615-5169) and are approved by the Army and the Marine Corps.

Being MIL-SPEC and being issued are two different things.

PMAGS are not MILSPEC nor are they STANAG 4179 compliant.

[Bolverk93]

Perhaps I should not have claimed the PMAGS to be mil-spec. I'm not prepared to argue what constitutes mil-spec or not. Regardless they are approved by the USA and USMC, which indicates a certain level functional testing with mil-spec weapons.

The purpose of this thread was really to make people aware of an existing issue.

*Edited to be more cordial.

Looking at MagPul's description of their M3 mags it states "the GEN M3 is optimized for Colt-spec AR15/M4 platforms".

Colt-spec is apparently now a thing.

I will stick with Colt and Daniel Defense from now on.

I'm not going to sign up for photobucket.com just to post pictures, but there is a discernable difference between my DD lowers and this BCM.

The DD lowers are flush with the trigger guard at the magwell. The BCM magwell extends a fraction of an inch below the trigger guard.

There is no wearing in of these mags to fit. Also, I have already run thousands of rounds through these mags in my work gun.

[Grip]

I have a KAC lower that does not accept NHMTG mags, but works with every p-mag I own.

[jethroUSMC]

Also the M3 magazines state that they sometimes need to be worn in a bit to fit all lowers. It took more than a few times inserting and removing the mags probably several minutes per mag until they fit in all of my lowers.

[Omega9]

Beat Trash had the same problem a few years ago.

https://www.m4carbine.net/archive/in.../t-169913.html

[officerX]

I have 2 BCM lowers and I use M3 PMAGs exclusively and have had 0 issues.

[MWAG19919]

My BCM has never had a problem with any of my Gen M3 PMAGs, but I'm aware of the issue. At one time I read the entire thread on here about it, and I really wasn't impressed with BCM's attitude toward the issue. The mil-spec excuse is pretty lame when Colts don't seem to suffer the same problem.

[ace4059]

Guys,
This is a known issue.
BCM has known about it for a few years and has done nothing about it. They blame MagPul and say there is nothing in the TDP as the length of the magwell where the over insertion tab hits.

If you ask MagPul then they blame BCM for out of spec lowers.

Basically you have four choices
1. Sell lower
2. Use different mags
3. File off tab on mags
4. File bottom of mag well on lower