AR15 POLY 80 lower failure?

[titsonritz]

The standard AR lower receiver does not work well when made out of polymer, as mentioned by @Stomper above they are weak were the receiver extension screws into the lower.

If you really got have a polymer AR look for a CAV-15:
Home of the CAV-15 MKII Rifle | GWACS Armory | AR-15 Lower Receivers
or pre-order a WWSD 2020:
WWSD 2020 – What Would Stoner Do 2020? – Q&A with Karl Kasarda
as they eliminate that connection.

 

[JeremyK]

I've got one of the Tennessee arms polymer lowers, and it broke without ever even being fired. I simply assembled it and the channel that the rear takedown pin detent spring sits in (the one held in by the stock plate) broke inwards into the trigger pocket. Seems that inside wall couldn't handle the stress of the compressed spring. I'm gonna send the whole thing back to TN arms when I get back home. Apparently their latest polymer lowers are a lot better, and where the buffer tube threads into the lower, there is a brass insert. Keeping my fingers crossed it doesn't take forever for them to replace it, because I need it for a cheap Franken-build.

 

[TTSX]

If you could buy an object you knew for a fact would be subject to shock force/ weird stress and you had the option of buying, at the same cost, a forged metal version, or a plastic version and nothing else was different, why would you choose plastic? Worth considering.

 

[andreys21]

Aluminum forged lowers are tried and tested, why take the risk? I'd use polymer for a .22LR build for plinking and that's it.

 

[DirectDrive]

Why polymer AR lowers generally speaking, are a bad idea :

1) Aluminum alloy lowers are inexpensive so there's no giant cost savings in favor of polymer.

2) The M16/AR15 lower receiver was engineered to be made of aluminum alloy.
This is the biggie and why all the polymer AR receiver fails happen.

 

[kmk1012]

If you could buy an object you knew for a fact would be subject to shock force/ weird stress and you had the option of buying, at the same cost, a forged metal version, or a plastic version and nothing else was different, why would you choose plastic? Worth considering.

Now, you are talking some sense! Kinda like comparing the crap we get and buy from China compared to a quality manufactured piece. Might be a couple more dollars but will last.

 

[turbo_vanner]

I have about 5k on one, its a lightweight racer type rifle. If it breaks it breaks, I'm not too worried about it.

 

[11Charlie]

Doesn't the word plastic say it all?!!!

 

[bbbass]

Great thanks! I've had one sitting around in my garage for a year. I've been wondering if the $80 for the lower is really worth the pain in the bubblegum to try to Mill thing out and get it working.

Not if you look at it that way. It's supposed to be a fun project akin to building a Colonial rifle from a kit. But I wouldn't spend money on milling tools for it.

 

[bbbass]

I thought the Polymer80 lowers were supposed to be thicker in the areas that poly lowers usually have problems.

Bought my first Polymer80 lower because:
1. I wanted a "ghost gun"
2. I wanted a fun project that could be done with minimal tools
3. It was dirt cheap - on sale for $50

I learned quickly that I didn't want to use a hand drill to mill it out because lack of accurate control over the drill makes/gives a shoddy looking result, and can result in thin spots. I had a bench press, so I bought a cheapo X-Y cross axis vise from Harbor Freight.. that was a bad decision... too much slop still.

Beware of using the drill bit that comes with the kit for trigger pin holes... a slightly smaller bit is needed to avoid making oversize holes. If you make oversize holes, do NOT use Loctite to lock the screw into a anti-walk pin. Ask me why... Okay, it's because the Loctite will completely MELT the polymer lower over a period of days!!! Ask me how I know. Polymer80 didn't like my complaint, but the non-specific warning is hidden in small print in the info... the first rep shined me on, but the bozz sent me a new kit.

Bought a second Poly80 lower in pink to build into an AR for my daughter. Neither of us have had any breakage during use.

Price compared to buying a complete aluminum lower does not compare well. The idea is to have one that is not serialized, and to have a fun project for those that like to tinker.

However, if I had to do it over again, I would spend the money for an aluminum 80% blank and a quality jig for that. The jigs are accurate, not expensive, and can be used multiple times.

 

[11Charlie]

3. It was dirt cheap - on sale for $50

I have three extra 80's sitting in my safe that were cheaper than that and they aren't polymer/plastic!!!

 

[bbbass]

I have three extra 80's sitting in my safe that were cheaper than that and they aren't polymer/plastic!!!

I bought my Polymer80 when those others weren't cheap. And jigs were not cheap, not perfected, and hard to find.

As I mentioned, I wouldn't buy a Poly80 today.

 

[wired]

I remember when you had to machine your own threads on the rear of an 80% what a PITA that was to get straight.

 

[deadeye]

Poly 80's are for the budget builders the Polymer 80 comes with the jig, drill bits and mill bit. Like stated above the aluminum were not so cheap along with having to purchase a jig which also was fairly spendy and not so accurate. All were originally made to use a drill press but now with a mini plunge router and a good jig come out pretty decent. Have to remember not everyone has a drill press or the extra funds to spend on tools and jigs. Some of the poly lowers now have metal inserts at the stress point and have been improved more than once to reduce the stress breaks. If you don't plan on doing more than one the poly is budget friendly but aluminum 80's are cheaper nowadays but the jigs/ bits not so much if you only do one. Yep you can sell the jig and bits to get back some of the funds afterwards just don't mess up the jig....

The poly's are good for .22 uppers and keep the costs down on a dedicated .22 AR just make sure you undersize the side holes and use a reamer to get to the needed sizes. I assume the pistol cals. would also work well with reduced stress on the tube area.

The whole idea behind them was to have a non serialized item and a fairly easy project to end up with a rifle that you made yourself. Never saw a Cav Arms type poly (serialized) as a benefit though, may have been cheaper but still wouldn't go there. Not everyone plans to run thousands of rounds through their rifle some just want to have one handy and the poly's fill that niche.

 

[DirectDrive]

I have about 5k on one, its a lightweight racer junker type rifle. If it breaks it breaks, I'm not too worried about it.

Fixed it

 

[Cracker]

Thank you everyone for all of the responses. A lot of good insight. Just received a shipment of .223 today! I can go shoot some paper tomorrow. I think I will post a thread about steel targets. I have never shot them.

 

[Cracker]

Fixed it


[/QUOTEThat's funny

 

[DirectDrive]

Thank you everyone for all of the responses. A lot of good insight. Just received a shipment of .223 today! I can go shoot some paper tomorrow. I think I will post a thread about steel targets. I have never shot them.

Set them back far enough so you don't pit them with your rifle.
I shoot my steel at 20-25 yards with pistol only.

 

[Cracker]

Set them back far enough so you don't pit them with your rifle.
I shoot my steel at 20-25 yards with pistol only.

Do you use standard FMJ ammo? Is there anything special about it. I can understand that it might be safer when you're shooting a rifle at a steel target that's 100 yards away. I was just wondering about the pistol shooting.

 

[DirectDrive]

Do you use standard FMJ ammo? Is there anything special about it. I can understand that it might be safer when you're shooting a rifle at a steel target that's 100 yards away. I was just wondering about the pistol shooting.

With pistol we shoot ball ammo (FMJ) and SD hollow points.
Range is 20-25 yards.
Plates are on chains, springs and/or hangers.
Never had any comebacks.