Polymer AR vs every other modern gun?

ericoak · Aug 6, 2016

So I find it pretty interesting that when given a choice between a polymer ar-15 lower receiver and an aluminum one, almost everyone chooses forged or billet aluminum. The market makes a clear choice that metal is better than polymer. But basically every modern gun (ARX160, SCAR, ACE Galil, Bren, Tavor) now has a polymer receivers. Now these guns are all based off of military guns, which have different priorities from the civilian market. But the Army isn't asking for new polymer lowers for their m4s either. So what is different between the m4 and all of the others that causes a flip flop in preference?

HordesOfKailas · Aug 6, 2016

This is an interesting line of questioning. Bump for my own curiosity.

blksniper2000 · Aug 6, 2016

I would assume because the others were built from the ground up as polymer versus converting over to it from metal like the ar15 but I'm really just guessing

Magnumite · Aug 6, 2016

I can only come up with rigidity affecting performance and dimesional stability. Those are both debatable but evidence exists. Good question, though

Boom Boom · Aug 6, 2016

I've owned polymer and aluminum AR-15 lowers for quite a few years. For the most part, polymer lowers are cheap and nothing else. They flex, bend, and crack. They can also warp. If (more like when) a polymer lower cracks, it's a coaster. If it warps, it's a coaster. Flexing and bending make them unreliable and often ill-fitting compared to aluminum. At this point, I wouldn't entertain another polymer. Aluminum is superior by a wide margin.

Ski169 · Aug 6, 2016

blksniper2000 said:
I would assume because the others were built from the ground up as polymer versus converting over to it from metal like the ar15 but I'm really just guessing

I second this. The AR platform wasn't designed with polymer receivers. The other platforms were designed from the ground up with polymer so they were built with that in mind.

sailskidrive · Aug 6, 2016

The design of the AR does not lend itself well to substituting polymer for aluminum in the lower receiver due to the stress points where the buffer tube screws into the receiver.

Additionally the only substantial benefits of using polymer are for either reduction in cost or weight. The aluminum receiver is already very light and polymer offers a nearly negligible weight reduction. As far as cost, with the quality gap narrowing significantly over the past 7 years between the low and high end manufacturers, the receivers have basically become fungible. Economies of scale with literally well over hundred manufacturers turning out quality lowers has driven the price down to the point where there really isn't a need for the minor savings polymer brings to the market...

Bertfish · Aug 6, 2016

I've been known to own a polymer-based firearm or two but some folks just trust metal over plastic

jimbobborg · Aug 7, 2016

If plastic lower receivers were $15 a pop, you could buy several dozen as throw aways and reuse parts. But they're not that much cheaper. In fact, the last time I took a look at plastic receivers, they were over $70 a pop. I can get an Anderson milspec lower for $55 all day long. If I wanted to shave weight on it, I can mill out sections in non-critical places.

Rack&Roll · Aug 7, 2016

Yup.

On the designs noted in the OP, there is so much more plastic buttressing the lowers in those models. More mass, more strength.

jawn · Aug 7, 2016

None of those plastic guns have a receiver extension, in which the bolt carrier cycles, thread into a relatively small amount of material.

shooter682 · Aug 7, 2016

The difference between the AR platform and the modern riffles is that they were designed from the ground up as a plastic receivers and the structure to support it. The AR design was for metal due to the design of the buffer tube, the other riffles have a structure to support the design. I have noticed that the Omni plastic receiver has an aluminum insert in the buffer tube area to address this weakness.

ericoak · Aug 7, 2016

Why not just used forged aluminum in the newer modern guns? Can't mill the internal cutouts they need?

Chris · Aug 7, 2016

I got a couple of polymer lowers and a couple aluminum both seem to work fine. I'm not shooting 1K rounds a month in any of them either. My goto rifle that I have shot the most is a RRA aluminum lower/Spikes upper, gun has close to 17K rounds so far and zero problems. If you are building a rifle that will be used for comp then I would go for the metal lower. IMHO Chris.

j_h_smith · Aug 7, 2016

I have a stash of polymer lowers on hand, just in case. Doesn't everyone?

mopar92 · Aug 7, 2016

The problem with MOST polymer lowers is the weak structural area where the reciever extension threads into the lower receiver. Two solutions one is to use a thicker amount of polymer or a different composition polymer. Or buy a GWACs armory polymer lower reciever that has the receiver extension made into it as an integral part of the lower receiver, the downside is you're left with a fixed stock.

smokey · Aug 7, 2016

I tuned in to Larry Vickers' live chat on the 4th and this issue came up. LAV was cohosting the chat with the product director from colt.
https://www.facebook.com/LarryVickers/?fref=ts
they talk about it around 14:20

...their conclusion was that polymer lowers can be made just fine to be plenty strong, but to make them correctly would put them at a higher price than regular aluminum lowers now. Basically saying, there are so many people punching out so many lowers that it's not economically feasible to go through all the R&D and tooling to produce polymer lowers to make it really catch on.

RoadDawg · Aug 8, 2016

Chris said:
I got a couple of polymer lowers and a couple aluminum both seem to work fine. I'm not shooting 1K rounds a month in any of them either. My goto rifle that I have shot the most is a RRA aluminum lower/Spikes upper, gun has close to 17K rounds so far and zero problems. If you are building a rifle that will be used for comp then I would go for the metal lower. IMHO Chris.

The last lower I bought before the F'n Suck Arse of 2013 was a New Frontier Armory polymer lower... I built it with PSA parts and took it to the range... No issues at all. I don't plan on chopping fire wood or jacking up trucks with it, so, it should be okay for a good long time.

TheBulge · Aug 8, 2016

ericoak said:
But basically every modern gun (ARX160, SCAR, ACE Galil, Bren, Tavor) now has a polymer receivers.

They might be covered by polymer parts but, Im pretty sure the Galil ACE, Tavor and SCAR have metal receivers.

.

ericoak · Aug 8, 2016

TheBulge said:
They might be covered by polymer parts but, Im pretty sure the Galil ACE, Tavor and SCAR have metal receivers.

.

Nope the lower receivers are polymer.

Polymer AR vs every other modern gun?

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