Is one considered superior to the other, or are they pretty much comparable?
I don’t know. The BCM comes with an H buffer (if that matters to you).
C4
I thought this was the case of most of the differences being in the RE. Is the LMT RE better made (stronger) Grant? I always wondered about their grey color.
Same material (7075). So they are equal I think.
C4
One thing I’ve always liked about the LMT RE is that they fit a little tighter in all my stocks than other mil-spec REs. I also like that the bottom of the bolt catch paddle is knurled.
This is true, the RE do seem to be a little tighter.
Pick whichever roll mark you prefer. 
I took mine out to compare them. The BCM lowers come with the Magpul MOE Trigger Guard, which might save you a few bucks if you were going to add one anyway. Comparing the triggers, I’d have to give the very slight edge to BCM. I think it feels a bit more crisp, but that’s entirely subjective. The LMT RE is slightly tighter on the normal M4 stock (which I never use anyway). The fit with my uppers is basically the same, yielding a slight bit of rattle with most uppers.
These are two of the most well-regarded manufacturers of AR components, and you will not likely ever have reason to regret either choice. So… yeah, as SWATcop1911 said, pick a roll-mark and run with it.
This is what I thought. Thanks for the help.
As was pointed out to me by Robb the LMT RE is thicker than most. It fattens up about a inch from the end plate.
I have had experience with LMT but not BCM. I am sure both are good lowers, same material. The LMT holds some government contracts and his held to a higher standard. Now that does not mean there is anything wrong with BCM though.
One thing I was disappointed with LMT is that they do not include the H buffer with their lower receivers.
You probably cannot go wrong either way.
I’ve seen 2 LMT lowers (admitedly a small sample) that would not drop certain PMGs free when you hit the mag release. If I remember correctly, this happened with ones other than the standard Black mags and with the windowed versions.
I have two LMT and one BCM lower and none of them will drop an empty PMAG but the BCM is much nicer than either of the LMTs but all work perfectly and that’s all that matters.
Rob_s posted a pic where to sand P-mag to drop free. https://www.m4carbine.net/showthread.php?t=30029
My Lmt will drop any window P-mags free with out sanding but some of the none window P-mags needed to be sanded to drop free. It was just a tiny amount took less than a minute to do each one.
The first ten Pmags I ever bought would not drop free from my LMT lower. I hit them with a little sandpaper and now they work fine. All Pmags I have purchased since then have dropped free without modifications but were nice and snug.
I was told Magpul tweeked the dimensions to fit tighter lowers. The newer Pmags have been tweeked again and fit like an aluminum USGI mag.
The ones I had to sand were date stamped 12/07 through 06/08. Any of the ones I have purchased since then have worked fine. This was a mix of windowed and non-windowed. I have around 75 Pmags now.
both are from very high quality companies. either one will do you well.
Yeah, the problem was not with your lower the problem was the older style PMAGS. I had some older ones that would not drop free from a Colt, Rock River, LMT, you name it. Just have to do the sanding fix.
All the newer style PMAGs have been fixed to solve this issue.
Now this is going off the Rifle chart that is so famous, but the BCM rifle has all of the same options as the Colt 6920, and the BCM is cheaper. The materials have the same spec’s down to the metal used. Is Colt just more because it says “Colt” on the side?
Rob_S (the chart maker) has expressed a few differences that are not on the chart recently. I believe they were mostly about the higher quality of the Colt receiver extension and maybe some small parts.
Can you provide a reference?
Thanks,
Jason