Polymer lowers on ARs...

[RogueUSMC]

Ok, searching the web and talking to people has led to a little more insight.

First off, the tag for an inexpensive polymer lower was on top of the Spikes billet lower in the picture above...and it was marked about $100 higher than the prices on Spikes' own website...therefore, no purchase made on a lower today.

But this has got me thinking of building one and it got me studying the polymer lowers.

Gripe 1: they break easier. I don't really think this is much of an issue unless you are abusing your rifle. And I don't think it will break much more than an aluminum would. With the exceptions of what I figure to be weak spots. The hinge area at the forward breakdown pin and the threads where the buffer tube/stock joins.

Gripe 2: and this would be the one I would think was relevant IF you ran it hard enough. When run hard, the barrel (being one alloy) will heat up differently than the nut (being a different alloy) which will heat up differently than the upper (being another alloy) and the lower heating up differently (being another alloy) all working together to throw the zero off when sustained fire is held. The polymer parts (that don't really 'heat up') make all this happen differently.

So with these two being the main gripes, I don't see myself running this gun to where either of these gripes would be all that relevant to me???

[psijac]

I have the same as baldeagle - haven't run it hard, but it's worked flawlessly so far. The polymer feels like a Glock frame.

[ Image ]

Pluses and minuses, hmmmm. Well, baldeagle bought his first during the recent Panic (when folks wanted $700 for a stripped lower, IIRC) and showed it to me; it looked strong enough so I bought one a little later. It's a plenty accurate rifle, not that the lower has much to do with that, but still.... I'm not sure what major benefit one would get specifically from polymer these days other than its inherent flexibility; it'll take more pressure by bending and springing back than aluminum will.

I have that lower. Had to replace the trigger/hammer because I was getting double taps from a single trigger pull

[Texsquatch]

[ Image ]

This is like the one I am looking at but I think the one at the gun show is sans trigger guard...I think Spikes makes it.

You may want to double check on the lower at the gun show. Your picture is a Spike's billit aluminum lower. I'm not aware of a polymer version. Spikes asks $300, who did the vendor say at the show?

[The Annoyed Man]

Gripe 1: they break easier........

You might want to watch this video in which a forged aluminum lower is tested to destruction in a press, compared against a polymer lower test in the same press:
[youtube][/youtube]

And as I mentioned previously, the FN SCAR uses a polymer lower from the factory. Now, it is a different design, but that lower does still encloses the magwell and the fire control group - both areas of concern if you were worried about the strength of a polymer lower receiver.

MY worry about polymer isn't whether or not it would withstand a short term beating in combat; it's about how it would stand up to long-term wear at the points were pins run through the receiver material. That may be a non-issue..........after all, it is a non-issue for polymer pistols......but rifles may be different, and the thing is, we just don't know. I don't want to be the guinea pig. OTH, I am already, a little bit, having just acquired an expensive battle rifle with a polymer lower........made by a company with a reputation for not making junk.

[RogueUSMC]

I would figure it was the polymer hammer...I would go metal hardware whether I did polymer housing or not. Plastic can't be expected to last long when it's purpose is to beat on metal...

[psijac]

I have the same as baldeagle - haven't run it hard, but it's worked flawlessly so far. The polymer feels like a Glock frame.

[ Image ]

Pluses and minuses, hmmmm. Well, baldeagle bought his first during the recent Panic (when folks wanted $700 for a stripped lower, IIRC) and showed it to me; it looked strong enough so I bought one a little later. It's a plenty accurate rifle, not that the lower has much to do with that, but still.... I'm not sure what major benefit one would get specifically from polymer these days other than its inherent flexibility; it'll take more pressure by bending and springing back than aluminum will.

I have that lower. Had to replace the trigger/hammer because I was getting double taps from a single trigger pull

Was that caused by the lower itself, or the hammer/trigger?

I replaced the plastic hammer/trigger with an ALG QMS with anti rotation pins. I have not been back to the range yets. I'll let you know

[bernard02]

I would figure it was the polymer hammer...I would go metal hardware whether I did polymer housing or not. Plastic can't be expected to last long when it's purpose is to beat on metal...

Even I myself won't go with polymer, because of the very reason that it won't last longer such as metal. Though it lightweight but still it doesn't my type at all.

[gljjt]

I would figure it was the polymer hammer...I would go metal hardware whether I did polymer housing or not. Plastic can't be expected to last long when it's purpose is to beat on metal...

Even I myself won't go with polymer, because of the very reason that it won't last longer such as metal. Though it lightweight but still it doesn't my type at all.

Kind of depends on the design doesn't it? My Glocks have been pretty darn reliable. The new Boeing 787 structural weight is 50% non metal (composites). Up from 12% with the 777. These technologies have advanced significantly in the last few years. To state that polymer lowers cannot be as durable or as reliable is anecdotal at best.