Polymer Lower Receivers? Final Verdict.

[Diamondback]

Personally, I would not even bother with a polymer lower. Unless you are building a dedicated .22LR rifle, stick with aluminum.

They do have a niche, but not so much in builds... they're great for cheap, disposable practice pieces learning to hog out a trigger pocket if you don't have prior machining experience.

[GSPatton]

I wouldn't turn down a polymer lower if it was given to me for free, but Aluminum ones can be found (could be, rather, lol, prior to the Zerg rush on lowers) for pretty darn cheap to make it a wash cost-wise

[themonk]

The polymer 80 ones suck. They have no steel or aluminum reinforcement. You would be better off doing a regular aluminum 80% and getting the router jig from 80% arms.

[HHollow]

I am a polymer engineer and I love plastics of all kinds. I agree that a polymer lower would hold up (longer) if designed from the ground up. However, I would not use polymers on anything I would need to still be functional after 20 years. Polymer simply does not age well. Oxidizes, stress cracks, embrittles, light induced decomposition, plasticizer migration, etc. Many folks who make thinks out of commercial polymer formulations have no idea what research is really necessary to show long term durability.

[kwg020]

Polymer lowers found a niche when aluminum lowers were very pricey. The price of aluminum lowers has dropped considerably from where they were just 6 years ago. I have a couple of polymer lowers and I have used them on builds. In 20 years they may get brittle and fall apart but that is OK. I will pull them apart and swap the parts into an aluminum lower. But, for a while they were the affordable alternative. We have no idea where America is heading for in the next 4 years. Unfortunately, we may need that affordable alternative at some point in the future. But for the most part, the R&D has been done. Americans can build usable polymer lowers.

kwg

[TED]

http://www.kearms.com/KP-15-polymer-receiver.aspx

You would probably have to talk to KE arms about getting a 80% though.

KE Arms has specifically said they will not be doing 80% versions.

I did prototype testing for Cav Arms back in the day and still have prototype # 6.

The Cav Arms aka GWACS and now the KE Arms updated versions are the only polymer lowers that I would trust for serious use. This is because they were purposely designed from the ground up to be made from polymer and the one piece design diminishes or eliminates some weak points such as the receiver extension mounting point. That last part is where most of the breaks on polymer lower occurs.

TED

[TED]

BTW, the CAV arms, GWACS to be sure, and I presume, the KE Arms are actually more durable in many ways than aluminum.

Look at some of the inrange videos for more info.

[ST911]

The Robar polymAR was pretty neat, and a good example of a polymer AR done well.

[okie]

If I were going to redesign the AR, I would definitely give it a polymer chassis, without a doubt.

That being said, successfully doing so would require a complete redesign. The cav arms lower is about the closest thing on the market to that, and it's a great product that definitely works. It's the only polymer lower I've seen that does. Unfortunately, they did a pretty crappy job of making it look nice and including features, like an adjustable stock, most glaringly. They basically could have made it a SCAR style lower, and probably even got it to fold. Not sure why they didn't.

[ST911]

Politics and ranting removed, let's keep it about the viability of polymer in the AR. Please stop turning every thread into a rant about this or that.

Offending content and replies removed.