My question is why do some of these top end manufactures who produce lowers that are supposed to be machined to mil spec wont drop certain pmags .....but all four Colts (The de facto mil spec) I have from 2009-2018 manufacture dates all drop everything. What specs are they using?? Are there paper specs that are tighter than what Colt actually uses?
I picked up a LMT Defender and a MARS lower in the last two years and neither will drop Gen 2 Pmags
"A flute without holes, is not a flute. A donut without a hole, is a Danish." - Ty Webb
I had to go look through my old posts to find it but here's a thread where I shared about a brand new 6720 vs 6920 with apparently different final mag well specs. Dec 2017. I don't own either of those guns at this point.
https://www.m4carbine.net/showthread...0-6920-quality
Not to further derail this thread, but it seems to be a Pmag problem rather than a receiver problem. I’m sure this has been discussed ad nauseum elsewhere.
Just tested a Noveske Gen 2 lower, and Pmag Gen 3 does not drop free.
Its a QC issue. If the magwell is at or over .91 you're not going to have any issues. I have not seen a BCM with a drop free issue, their issue was with the pmag gen 3 over insertion tab bottoming out against the reciver.
Noveske learned they had an issue with the Gen 2 and they fixed it. LMT, Colt, KAC ect.. the issue is they dont care about that spec (saying they go off metal GI mags) and you can get lower that are .90 to .92
Dunno. Seems to be a mostly a boutique company issue. Usually brands that I have very high expectations of. Couple days ago, I took a G3 PMag, wrapped it in wet/dry sandpaper and crammed it into a *** stripped lower, no lube, like a hundred times. Still doesn’t drop PMags, and neither does my ***************. They both toss GI mags perfectly. I’ve got a few other brands that are tight, also.
One, out of maybe 10 or 12, Aero strippers has been tight, but a few mag changes cleaned it up. Zev has the nicest magwells I’ve seen on any forged factory lower of any type, anywhere. I would assume that Mega’s, etc, are similar. Grey Ghost Precision also has a nice magwell.
I’ve heard they exist, but I’ve never personally encountered a Colt that wouldn’t chuck a mag. To be fair, almost every Colt I’ve ever put to work has been reamed out by a series of enthusiastic 20yo kids for a decade plus. The 4 Centurion lowers I own are indistinguishable from Colts in any way I can detect, except the rollmarks.
Edit: cleaned up because I don’t want to start any shit, particularly with individuals or companies I generally like.
Last edited by 1168; 10-29-20 at 16:36.
FWIW, I just picked one of these up yesterday, PMAG M3's fit perfectly. A little spendy, but a nice lower.
Sorry for the necro thread, I just wanted to add my recent experience to the thread.
I was finally able to assemble the stripped BCM lower that I bought from the link in the OP this weekend.
I bought a complete BCM® MK2 BFH 16" Mid Length (ENHANCED Light Weight) Upper Receiver Group w/ MCMR-15 Handguard to put on top, but wanted a stripped lower so I could add parts that fit my physical limitations and not have to throw away the stock parts.
To be honest, you are paying for the name/roll marks on these is all.
The mag well works fine on mine with 10, 20, 30 round PMags, but the upper lower fit is very sloppy (worst I've seen) with no way of adjusting fitment.
I did not use any cheap/bargain parts, so I am a little disappointed with the build over all, but hey its just money, right?
A BCM ambi charging handle would not work so it will be sent back to BCM as defective, I had a spare non ambi BCM in the parts bin and that one worked just fine..
I also build an Aero M4E1 upper/lower this weekend for my wife and the Aero fits better/tighter than the BCM and has a couple threaded spots for screws to make installation easier, so the $100.00 difference in the two lowers is only for the name/roll marks.
Like other have already said, unless you must have the roll marks, buy a cheaper lower.
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