Lubricant choice will be the most important for cold weather function.  I did a bunch of testing at -10F last winter and found huge differences between different lubes.  The nature of the AR15 design means that a lube that goes very sluggish and increases drag in the cold will induce malfunctions.

RCMP did a bunch of cold weather lube testing a few years back on different lubes and IIRC the AR15 platform was one of the test firearms. And when the RCMP tests "cold weather", it's colder than you'll ever see in Ohio.  IIRC -60 or -70F.

Google will probably reveal the full information on the tests.  From what I recall EEZOX was the top choice, with TW-25B, FP-10, and one other on a "suitable" list.  TW-25B is one of my favorites anyway so that is what I normally use.

I just had another thought.  Could the O.P.'s guns have not been broken in prior to the cold weather shooting?  I'm just thinking that new anodizing, parkerizing, etc, aren't the smoothest surfaces.  You really notice the smoothness in a well broken in AR.  The malfunctions may have been caused by the combination of a lack of break in, the poor lube choice, and maybe underpowered ammo like wolf.

+1

I use a 50/50 mix of synthetic ATF and synthetic motor oil and have no problems in extreme cold conditions. If you are shooting during severe weather and the bolt freezes closed, you can free it by simply mortaring the rifle a couple of times. Just make sure your buffer extension is decent quality. I get a kick out of the guys who swear their commercial extensions are "just as good". Apparently they have never freed a frozon bolt-when they do they usually come around. Particularly when they are on their hands and knees picking up the broken pieces

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I would agree if the AR was the only one in the group that was not lubed but all the rifles were treated the same. Again the test was performed to bring out any weakness in the platform. Basically it didn't tell us anything that isn't common knowledge. The Galil, FNC, Valmet are superior to the AR and even AKs when it comes to robustness and they offer the accuracy of an AR.  If Bush had not implemented the importation ban I'd imagine they would be a affordable common item in gun safes.  Even with lube the AR is more prone to fail in extreme cold than any Kalashnikov rifle. Again, common knowledge.

But all this is moot as the OP wants an AR that will perform reasonably in extreme cold. With a few extra precautions this can probably be achieved with the already mentioned methods being correct lube and NiB coating. It's not going to transform it into the realm of top tier Kalashnikov robustness but should make it perform at an acceptable level.

Again, I'm just stating well known facts. I love ARs. The majority of the time they will go toe toe with anything out there if properly maintained. Sometimes optimum maintenance isn't an option though. That's where these other rifles pull ahead a bit. Unfortunately with the current importation ban they are not a realistic option due to cost. And only the 5.56 Galil has easy to acquire parts and mags.

Being the OP wants to utilize the plethora of AR mags he has, any of the commonly known quality ARs with right lube and surface treatment on moving parts should perform acceptably well.