Polymer Receivers

[wch]

There's something about the innate strength and/or durability of AR-15 plastic receivers that makes me distrust the idea.
Anyone have experience with them, anyone with a list of pros and cons?

[Winger Ed.]

Modern generation plastics are pretty incredible.
Back in the 90's one of the auto makers built a running prototype car engine that didn't have any metal in it.

I had to make an exception for my Springfield XD, but I never warmed up to Tupperware guns either.
I haven't been around a plastic AR, but they would probably have been fired a million times before they went into production.

[VariableRecall]

Considering that someone has been able to make one-off lowers out of lego blocks and screws, you can make a lower out of just about anything you could imagine that's somewhat solid.
I suppose that the difference really is HOW long you want it to last.

Lego Block AR Lower Firing a full magazine without issue
https://youtu.be/Z4KQZ0LJwuY

Lego Block AR dissasembly
https://www.youtube.com/watch?v=OiqfTG2oF4s

[recumbent]

History of Monolithic Polymer ARs. Interesting video.
https://www.youtube.com/watch?v=RFxN...rgottenWeapons

[rancher1913]

well just consider all the real work is done in the upper, so the lower just has to support the trigger pins.

[Lloyd Smale]

not much stress on an ar15 lower. You probably could make on out of paper Mache and it would work.

[MrWolf]

I got one maybe 6-7 years ago. Shoots fine, no issues but I still prefer metal. No valid reason at all. Like others have stated only holds the trigger. Come to think of it think it is a full lower with an A2 stock style.

[DanishM1Garand]

https://youtube.com/playlist?list=PL...e3yXtez7CwkW8c

Gun Jesus and Gun Satan did a project where they built a rifle on a new polymer lower. This lower uses the strength and weaknesses of polymer.

I built one on the precursor lower sold by Armalite made by CavArms. It is a sturdy little carbine. I would avoid any of the polymer lowers that are a direct copy of an aluminum lower. These are prone to break.

[Blanket]

buffer tube area is the weak spot

[Petrol & Powder]

well just consider all the real work is done in the upper, so the lower just has to support the trigger pins.

/\ YEP /\

It's sort of a fluke of American gun laws that the lower receiver of an AR-15 platform is the "receiver" (controlled part) and the upper receiver that contains the pressure of firing is an uncontrolled part.
In other countries, the pressure bearing parts are the "gun".

The lower receiver of an AR-15 doesn't have much stress on it.

[RU shooter]

Unless your gonna be bayoneting or butt stroking something to death IE full on combat use , their plenty strong for what they need to do for 99% of civilian use . Can they break ? Yep so can an aluminum lower if you torture or abuse it enough. As been said about the connection of the stock tube is the weak link but some companies have beefed this area up and inserted metal reinforcement

[HATCH]

The issues that people have run into using the plastic lowers has been the buffer tube area but that is mostly when used in pistol caliber setups.

[Texas by God]

I've used a few of the CavArms type with no problems. My .300BO is built on one and it is as solid as my conventional ARs plus it fits to the upper with NO rattle. I like the light weight, too. Ugly as a mud fence but 8# with 30 rounds and a scope.
I'm leery of the conventional type polymer lowers, but haven't owned one.

Sent from my SM-A716U using Tapatalk

[fcvan]

I have built a couple with both materials, nary a problem. I saw one that I found interesting, the lower, grip, and rear A2 style stock was 1 piece. It looked pretty healthy considering the buffer tube was integral in the fixed rear portion.

I considered building one with a fixed magazine and a pump action just to P.O. the CA legislators. Fed through the ejection port with a device made by a manufacturer in SO CA, who also did so just to P.O. the CA legislators. The rifle was as fast to reload as a detach mag, maybe slightly faster as there is no mag to detach. The drawback was I needed to use an 18" barrel cut/crowned without threads, spendy to order a custom with a rate of twist just for cast.

I may still build a pump upper with normal parts and weld on the flash hider, or machine one with closed ports. For now, whenever I am in CA, I just shoot the Mini 14, having removed anything 'black and fun' from CA after I retired . . . from Law Enforcement. Our 'SWAT' duty rifles were AR 15s (former team member) and the regular duty rifles were Mini 14s. Fun thing is, the agency was set to transition to AR 15s due to their price, ease (and price) of maintenance, and accuracy.

I don't have a preference of aluminum or polymer, both work fine. I do know a guy who blew up an AR 9mm on a poly. He didn't use the heavy buffer which allowed the bolt to blow back before chamber pressure was reduced. Mag well and adapter cracked and ejected the magazine and parts at his feet. He described his upper as being filled with brass confetti. He ordered a heavy buffer and fixed the lower with Super Glue Gel. He said 'isn't that what Super Glue is for?'

His catastrophic failure did not result in injury nor was it caused by defective parts, only due to improper assembly. I built one with a poly frame, proper buffer, a silicon buffer bump, and a slightly stiffer buffer spring. Runs like a champ and is my favorite plinking rifle.

[Big Tom]

I 3D printed a few to play with it - weakest link, as described here already, is the buffer tube attachment (the ones out of plastic that you buy most likely have some metal there to make it more sturdy. Here's a pic of a 3D printed one, cost of material is about $7. It worked fine, but I am more of a fan of something more substantial as well.

[leadeye]

3D printing is something I've always wanted to try for hard to find parts on old guns. There are a lot of parts that just move around and keep things in place that don't get heat or stress, but are made of unobtainium today. Places like Jacks First does a pretty good job, but he doesn't have everything and what he does have isn't cheap.

[monadnock#5]

Strictly utilitarian works for me. I love my S&W 15-22.

[VariableRecall]

3D printing is something I've always wanted to try for hard to find parts on old guns. There are a lot of parts that just move around and keep things in place that don't get heat or stress, but are made of unobtainium today. Places like Jacks First does a pretty good job, but he doesn't have everything and what he does have isn't cheap.

I've heard that using 3D printed parts for such things as en-bloc clips have been fairly successful for rifles whose original parts are rare and hard to find.

[Lloyd Smale]

I 3D printed a few to play with it - weakest link, as described here already, is the buffer tube attachment (the ones out of plastic that you buy most likely have some metal there to make it more sturdy. Here's a pic of a 3D printed one, cost of material is about $7. It worked fine, but I am more of a fan of something more substantial as well.

to bad you cant sell those. Youd make a killing right now.

[Big Tom]

I would not even want to get into that - they really aren't as sturdy as the ones made out of enhanced injection molded plastics - and if anybody really wants to get into it, a printer is below $200, plastic is below $20 for a 2 lbs roll (probably good for 3-4 of these receivers). The design files are readily available on the internet for free...

On a side note - if anybody needs small parts they have the exact measurements for, feel free to reach out to me. As long as they are legal to make and I got time at hands, I am more than happy to see if I can help.

to bad you cant sell those. Youd make a killing right now.