What are your thoughts on polymer AR lowers?

I was at a gun show awhile ago, and a guy from cripple creek was selling complete AR lowers, ready to bolt an upper onto, for $149. I noticed that instead of the usual aluminum, they were polymer, and so were the internals. Made by a company called Plum Crazy Firearms of Lake Havasu City, AZ, and have a lifetime warranty.

I figured for $149, what the hell, how bad could it be. They said any issues with it, I get another replacment, no questions asked, and FWIW, it WILL accept regular metal MILSPEC internals.

ANyone have any experience with these? I haven't had a chance to shoot mine yet.

hmmm idk if i would go with polymer. just dosnt seem right. let me know how it does tho im curious

I've seen a heard of a lot of good reviews. Heck if Aluminum works for the receiver, a composite should be fine. Not to sure I would trust composite trigger group because those are usually steel and normally wear.

You can get em for $130 from a dealer associate of Plumcrazy's in Lake Havasu. $150 at the show with no FFL is good.

They're almost completely polymer - including the fire control! As crazy as that sounds, it's actually really robust and reliable, and the trigger feel is excellent. I ran through probably 1k rounds through mine and double that in dryfire (despite the manufacturer's warnings not to dryfire - maybe they meant without an upper attached). I'd still have it, were it not for my friend's desire to get started in ARs as cheaply as possible. It's still running well for him. Just check at the show to make sure the buffer tube and stock are solid, because I believe some of them are attached by the end dealer, which leaves room for variation in quality.

Two minor bits that vary from usual AR operation: The front pivot pin is flush with the receiver, so you need a bullet to push it out. Also, the safety can be engaged without the hammer being cocked.

I wouldn't use one of their lowers for a fighting rifle, but for a beater or cheapie rifle, they're more than robust enough.

They have my recommendation.

YEa, I bought 2 of them, one i'm gonna test as is, the otherone, I have a spare DPMS parts kit i'm gonna install in it, and see how both of them hold up.

IIRC the Plum Creek units are what used to be Cavalry Arms.

There supposed to be very reliable from what I've read. We will be doing a build for a customer soon. I will let you guys know how it works out.

I've been interested in these for several months and have been too afraid of them due to concerns of holding up to the concussive effects of firing and general wear.

It sounds like (from the experience of members here) that my fears are unfounded. I think I'll get one or two (not right away) and try them out as well. I've been wanting to build a cheap (yet safe) AR for my son and this just might be the solution.

Are they specific about use with .223 versus 5.56?

I would like to know the molecular structure of these before I bought one. If it is some injection molded polymer made from recycled milk jugs or something I would pass, that's just me though. If the parts are machined out of either Delrin or UHMWPE, then it might be OK. Delrin is great, but I have also seen it catch fire many times much easier than the UHMW. The UHMW on the other hand is better at impact strength and such, also has a much higher melting point (these are hot gas action guns), but scratches easier. I would like to see a stress test on one of these firing a few hundred rounds pretty quickly to see what happens. Might be a good use for a dedicated .22 upper.

Don't have any experience with the AR lowers. However, we've had polymer pistols for a long time now and these were the very same arguments against them in the beginning...and still today. Considering the recoil is all managed by the upper I would imagine there's even less wear and tear on the lower than there is on a polymer pistol. With a pistol the slide is recoiling against metal embedded in polymer which would seem to be much worse than a bolt reciprocating above a polymer lower.

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Originally Posted by theGinsue

I've been interested in these for several months and have been too afraid of them due to concerns of holding up to the concussive effects of firing and general wear.

It sounds like (from the experience of members here) that my fears are unfounded. I think I'll get one or two (not right away) and try them out as well. I've been wanting to build a cheap (yet safe) AR for my son and this just might be the solution.

Are they specific about use with .223 versus 5.56?

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the only wear issues would be at the H/T/S pins and take downs. Yes you have movement in the buffer tube area. Every other wear issue is related to the function of the upper.
The SO's build is a CavArms lower onn a lightweight bushy upper. have not had any issues even when shooting suppressed. I did find by notching the buffer retainer i did not experience the issue of the buffer riding over it.

As somebody who sees ARs in all lengths of service, I can say the vast majority of AR owners don't ever wear out a lower. If these lowers have have the life of an aluminum lower they will be fine for 75% of AR owners.

Just to clarify - these are not at all like Cavarms lowers. Cavarms is pretty proprietary, with integrated pistol grip and stock, and funny takedown pins. Plumcrazy (not creek) lowers are essentially like conventional Aluminum lower receivers - they use the buffer parts, trigger pins, metal bolt catch from a regular AR, but everything else is polymer.

The receivers are definitely not machined plastic chunks, not UHMWPE, and not delrin. They look to me to be glass-filled injection molded nylon (a pretty wide range of materials). I don't recall perfectly, but I feel like the firecontrol had a more "greasy" feel to it - maybe UHMWPE there.

I was quite skeptical (especially of the plastic FCG) when I first purchased mine, but it worked very well.