So I decided to get a polymer lower as a project (yes I kind of regret it now but it is what it is.) I knew I wanted to do a pistol build and I was planing on going with .300 BLK. Then I thought about a 9mm upper since I have a decent amount of ammo and .300 is a bit expensive. I read on another forum that 9mm wouldn’t be good on a polymer lower because it’s blowback operated and would stress the lower more than .300. Any thought or helpful insight?
I would only trust a polymer lower for .22. Certainly not for 9mm/40/45 blowback. Your other option is to hold and see what kind of legislation Xiden tries, and then sell.
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My only advice is to run it on a training gun only. Leave the defense setups with proven aluminum receivers. No worries that way, regardless as to what you decide to build it into.
I have 4 FMK polymer lowers on everything from a 10.5 762x39 to a 20" 6mm ARC. I really like them and have thousands of rounds through them. When things return to normal I’ll probably build a couple( I do 2 of everything) of 6mm Creedmoor’s. If I run across a polymer lower at the right time and price, I’ll buy it!
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I built my 5.56 PSA kits on 80% polymer lowers from eparmory in Burnett, TX (near Austin). They sell for $30 each. (shipping time is about 12 weeks, so I drove there from San Antonio to pick mine up)
Have fired about 200 rounds through them so far - and the owner said to do a full mag dump whenever I want to test them out against aluminum.
Prior to doing this, I did read some things on the internet about polymers failing - so once built, I carefully inspected them after the first shot, then after each magazine and again at home while cleaning. They seem to work fine, and I’m not a hunter or a sport-target shooter. These are for defense purposes.
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No offense intended at all… but admit defeat.
I did with my Carbon 97s … I turned the lower into a dedicated 22LR carbine.
Quite honestly it is an awesome lightweight 22LR . Works very well while Sage Rat hunting.
I also think the battering from a 9MM blowback would make most polymer lowers fail quickly. My Colt Pattern Blowback cycled far harder than any of my AR15 5.56’s
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I have a KE arms KP15 lower that I want to put the FN barrelled lightweight 14.7" upper on. Does anyone have any experience with the KP 15 lower and PSA uppers ?
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I have a JMT one with about 1000 rounds through it and no problems. I even did a couple mag dumps. No signs of cracking, melting, or anything else so far. Mine is using a 16 inch 5.56 upper with a mid length gas system though.
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KE Arms is the only Polymer lower I would currently trust.
I see no reason the FN Barreled PSA upper wouldn’t work. That upper is completely GTG.
I don’t have a KE Arms poly lower, but I do have that same upper. Heckuva deal for a CHF CL Nato spec’d barreled upper.
Please let us know how much you enjoy it !
Polymer lower is not the move as many on here have stated. Look around and you should be able to find a metal one for a decent price.
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I got one of those Omni hybrid lowers years ago, but the gun has been baby’d. Regret it now… Been waiting for the madness to slow down and will be picking up a replacement. This one will sit in the safe for a backup.
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I’m really glad to read that you have 1000 plus rounds through yours. I got 2 of JMT hole line up. I have not fired any of them yet. You the first I have come acrossed with over 1000 rounds. Thanks for the good new.
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I haven’t heard a single bad review of those KE lowers. I ALMOST bought one a few weeks ago. I may still get one in the future. Someone is having a blem sale on them right now (stripped).
I’ve purchased most of my lowers from PSA and I’ve also used a few from Anderson.
Almost two months ago I took a gamble and ordered several polymer AR-15 stripped lowers from Tennessee Arms. They took much longer to ship than I was anticipating, but yesterday I was informed that they have arrived at my FFL. I’m going in tomorrow to fill out the 4473.
I wish I had actual experience to share, but so far I do not. I’ll update here as I begin to use them.
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The Tennessee Arms stripped lowers are in my possession, and here is the weight compared to a stripped PSA lower.
The TA lower includes a screw for the grip, and has an enclosed trigger guard.
I’ve included a screw and trigger guard with the weight on the PSA lower.
I really like the idea of them being lighter. I have no idea about durability, or even fit, at this point. More to come as I learn more.
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For certain, I will use one for my AR-22, and most-likely for my 14.5" recce rifle I’m piecing together.
I think I’ll use one for a 10.5" pistol and try to most of the abuse on that one to see if it fails soon.
Overall, I’m not that worried about it failing. I have concerns with how it lines up with mil-spec uppers, but I’ll have a good idea on that tomorrow morning.
I did purchase 2 AR-10 lowers from Tennessee Arms, but it will likely be several months before I begin working on that.
Eventually I’d like a lightweight and short 300 Blackout for home defense, but I know that will receive more abuse than longer, midlength gas rifles.
My girl has plans for a 450 bushmaster, and a purple lower I received is dedicated to that. I’m interested to see how that turns out.
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I’ve pieced together this lil’ buddy to throw in a get-home bag.
*Tennessee Arms polymer lower. $42
*Cheap lower parts mostly sourced from UnbrandedAR. ~$35
*Chinese SBA3 knockoff. $10
*Chinese buffer, spring, tube. $8.50
*AR Stoner upper and parts from Midway. $78
*AR Stoner 10.5" 1:7 5.56, plus Midway block and tube. $160
*Toolcraft BCG from PSA. $100
*Lightweight handguard from OhHunt. $28
*VG6 Epsilon brake, a discontinued item at Fleet Farm. $40
*Iron sights off of Amazon. $18
I know there are better prices available for components for people who are dealers or those who buy in larger bulk than I do. I did get a slight sense of satisfaction knowing that this pieced-together pistol shoots as straight and as reliably as my $1000 weapons, at least at 100 yards.
(Oops, I forgot, I didn’t include shipping costs (when applicable) for the parts, so I guess this puts the overall cost up to almost $600.)
The overall point being that in this case, the polymer lower seems to be working alright. I’ve run only about 150 rounds through it, but I’ll continue to take it to the range to train with, and look for unexpected wear and tear each time. For now, I’ll keep cleaning and putting it back in its role as a (not likely to be needed) take-down gun for my get-home bag.
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I have a old school Plum Crazy that I have mated to a Chiappa deticated 22 upper, light and inexpensive, but could take a normal upper if it really hits the fan
Depends on the plastic used.
Some engineering plastics are very rugged, e.g. Torlon, PolyAmide-Imide.
Tried it for some electrical parts for a high frequency oscilloscope in the mid-80’s. We needed a plastic that could be soldered without sucking up too much heat, so plated Torlon worked good.
They used it build an Auto engine, it’s good to 537 F.
But when it comes down to it - Aluminum is sort of like an Extreme High Performance thermoplastic (can be melted & molded, not a thermoset.)
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