Have one with a BM carbon upper. Super light 5 pound AR. Even has decent trigger !  Research reveals nothing about them.

Anybody know about them ?

It'll work.  Until it doesn't.

A polymer lower is one thing, but think about a potential case rupture 8" from your nose where the only thing between your face and the chamber is a 1/8" thick piece of plastic...

I've got one on a dedicated 22 build and it is fine for that. I don't trust it with centerfire.

Had one, 7yrs ago I believe, right when they came out, topped with RGUNS m4 upper. At the time it was the cheapest AR I could get put together, $450. Put 300rds through it and sold it promptly for $650. Zero regrets. The company went under/ changed names/ sold out or whatever and the new company was new frontier armory who still make the lowers with new markings. Good thing they didn't hedge their bets on poly lowers, they make nice billet stuff also.

JB weld.....good as new....

At prices these days....................

All I can say is

WHY?

Carbon/poly AR.

Google BM carbon upper.
Then Google poly AR lower.

And then Google AR-15 KABOOM.

I had one that worked great for years. Even had a polymer trigger and hammer. Ended up selling it to a coworker. He is happy with it. They say lifetime warranty but I don't think they are in business anymore...

They are still around or back? http://e3arms.com/
Bought one of these complete lowers for a dedicated 22 build, works fine for that. Good customer service, quick to respond to emails & he sent me a 22 hammer for free after contacting them about an issue. Decent trigger for being a polymer FCG. Poly buffer tube though.

Thanks, I know they had some issues with the serial numbers being able to remove w/o disabling the lower. Mine has worked fine and I see the new maker is selling them for $100.

100$ for a completed POLYMER lower? Why? You can get Anderson Lowers for 40-50$, Hell I've seen them for 35. Get a parts kit for 40-60$, and a buffer tube kit for 30-40. Most is 150$ if your lookin in the right places it can get down considerably, I bought used parts from the EE, and finshed a lower for 100$ including the lower. For the extra 50-70$, it'll last a lot longer, and you won't be wondering when it'll break.

Primary Arms has a hell of a sale going on right now:
Lower - 30$ Lower Link
LPK - 30$ LPK Link
Buffer Tube Kit - 35$ Buffer Tube Kit Link

Thanks, I think you just started another build

Don't really see how that lower failed due to a case rupture, bolt is locked into barrel extension.

Thanks for the info. Mine has seen many, many rounds with a Bushmaster carbon upper w/no issues.

Would need the rest of the story on these failures to conclude it was the PC lower's fault.

I don't believe any of those were catastrophic failures, just plastic failing as a substitute for aluminum. The only satisfactory plastic lower is the Cav Arms one, because they understood that they'd have to redesign for a new material.

Lol, here we go again. New guy comes on board and asks about a junk product, with an attempt to validate his fondness of it.

ARFCOM members come out in spades even with images as evidentuary material of said junk product. New guy then attempts to argue the validity of this junk product.

Polymer lowers suck. You're attempting to fit a square peg into a round hole. The thicknesses of the material on the trunion, etc. were engineered for a different material, otherwise if the original designer were working with polymer, the parts would be dramatically altered to accommodate, and in the end would still be junk.

I don't recommend poly lowers either

Had a Plum Crazy & New Frontier poly lower, the NFA FCG failed and sheared it's pivot retaining pin. The Plum Crazy lost half it's grip threads last time I swapped grips.

if you're running a Plum Crazy on a Carbon 15 upper I'd worry more about the upper failing than the lower. it may run for years with no issues. But a few years ago someone posted a picture of their shattered Carbon 15 when they tripped and fell on it and destroyed it.

Plum Crazy was the first to make a poly lower that was a duplicate of a mil spec lower (unlike Cav Arms which was a proprietary design and stronger). This was back when a complete PC lower was $99 and a complete RRA lower was $250-$300. They got in to a lot of trouble when someone figured out how easy it was to remove the serial # plate from their lower. I think they redesigned it so you'd destroy the lower if it was removed but not too long after that they changed their name to PCM. Around the same time New Frontier started making theirs. Not sure how the two companies are related. I've heard PCM is still around.

Pretty sure Bushmaster had both of them beat with the carbon15

I wonder is a sticky would be obvious for new members to look at?

I have one with about 700 rounds through it, no issues.  This is on a 4.75lb 16".  I could go lighter, but then would have to start cutting/drilling stuf, or pay big bucks for titanium.

The vast majority of failures I have seen are people treating it like aluminum when doing things like shotgunning or but stroking, things that even break 7075 lowers.  I certainly wouldnt use it for anything but a range toy.  Handles and transitions targets like a nerf gun though, fast.

Price is irrelevant, these are there for the weight loss.  The tradeoff is durability.  My very small daughter can actually lift this one and use it, which means I can get her started shooting a 'real' rifle sooner.

If you really need a lightweight rifle that someone may have to actually use outside the range, and age, disability, or other means that low weight is absolutely critical, the brass/poly hybrid lowers out there have a good rep.

For me, it's hard to justify the cost of most poly lowers these days when you can buy an Anderson on Tactical Machining lower for $49.  You can trim weight in other ways than sacrificing it on a critical component such as the lower receiver, however if you fele you must go with a GWACS Cav15mkII lower.  Weight is also reduced in their design by integrating the stock, grip buffer tube into the receiver.  Less external hardware to worry about as well.

Before calling me a hater, I actually purchased a Plum Crazy lower back in 2011 for $100, at a time when alloy receivers were running for $150 or more.  I ran it on a build with an A2 stock, so stress on buffer tower was minimal compared to that of a collapsible stock.  Soon afterward I began seeing all the pictures of cracked receivers, then migrated the lower to a dedicated rimfire build.  I also own a couple of GWACS lowers (purchased when alloy receivers were unobtainable in 2013) and they have held up very well.

Go with a TNARMS lower if you want a polymer lower.