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Polymer AR Lowers
- Thread starter cmdc
- Start date
Don't really have any experience with them. I have read, however, that they're prone to breaking. Generally near the receiver extension if I remember correctly.
There is no benefit in my opinion to using a polymer lower.
As others have mentioned, you can get aluminum lowers for around $50.
There is no benefit in my opinion to using a polymer lower.
As others have mentioned, you can get aluminum lowers for around $50.
TrueBlue711
New member
I have 3x and I'm turning into a fan. Look up Tennessee Arms Co (www.tnarmsco.com). They're going as low as $32 with engraving on it, color choice and they have marine-grade brass inserts for where the buffer tube and pistol grip screw into to address any concerns about those areas breaking.
Here's my view on pros/cons of poly lowers (namely TN Arms):
Pros:
*Cost effective. Costs even lower than the $50 aluminum lowers.
*Corrossion. Will never happen...though I'm not exactly worried about aluminum lowers rusting either. But you'll never have to worry about finish rubbing off (unless you paint it another color).
*Fit. From the uppers I've attached (DPMS, Radical Firearms and Colt), the fit is tight. No wobble or wiggle what-so-ever.
*Weight. I haven't compared the two, but I'd guess they're about the same as aluminum lowers if not lighter. TN Arms advertises theirs as 5.6 oz
*Trimming. If the lower needs to be trimmed anywhere for fitting of anything, you can dremmel/sand down what you need easier than an aluminum lower.
*Lifetime warranty. If anything happens, send it in and they replace it, no questions asked and no cost. I had to do it myself when I accidently cracked the magwell trying to unscrew the barrel nut. Sent it in and it came back about 12 days later.
Cons:
*Fit. Could be a con as well as a pro since it is so tight, depending on your point of view. Difficult to quickly swap uppers if you're looking to do that in a hurry. It takes more force and a bullet or punch to push the pins out where my aluminum lowers can be taken down with just my fingers.
*Strength. While they are really strong, they may not be quite as strong as an aluminum lower. As mentioned above, the magwell did snap while it was on the vice block during my barrel nut removal. That being said, I applied a LOT of force trying to get that nut off (full body weight...not a good idea no matter what lower you have on. Damn my stubborness).
In summary, I would suggest at least checking out TN Arms. I have a New Frontier Armory poly lower as well, but I like TN Arms much more. With the lower costing almost as much as the transfer fee, I'd get one to just try it out. If you don't like it, re-gift it to a family member or something. Just an opinion of someone who owns both aluminum and poly lowers. Let me know if you have specific questions.
Here's my view on pros/cons of poly lowers (namely TN Arms):
Pros:
*Cost effective. Costs even lower than the $50 aluminum lowers.
*Corrossion. Will never happen...though I'm not exactly worried about aluminum lowers rusting either. But you'll never have to worry about finish rubbing off (unless you paint it another color).
*Fit. From the uppers I've attached (DPMS, Radical Firearms and Colt), the fit is tight. No wobble or wiggle what-so-ever.
*Weight. I haven't compared the two, but I'd guess they're about the same as aluminum lowers if not lighter. TN Arms advertises theirs as 5.6 oz
*Trimming. If the lower needs to be trimmed anywhere for fitting of anything, you can dremmel/sand down what you need easier than an aluminum lower.
*Lifetime warranty. If anything happens, send it in and they replace it, no questions asked and no cost. I had to do it myself when I accidently cracked the magwell trying to unscrew the barrel nut. Sent it in and it came back about 12 days later.
Cons:
*Fit. Could be a con as well as a pro since it is so tight, depending on your point of view. Difficult to quickly swap uppers if you're looking to do that in a hurry. It takes more force and a bullet or punch to push the pins out where my aluminum lowers can be taken down with just my fingers.
*Strength. While they are really strong, they may not be quite as strong as an aluminum lower. As mentioned above, the magwell did snap while it was on the vice block during my barrel nut removal. That being said, I applied a LOT of force trying to get that nut off (full body weight...not a good idea no matter what lower you have on. Damn my stubborness).
In summary, I would suggest at least checking out TN Arms. I have a New Frontier Armory poly lower as well, but I like TN Arms much more. With the lower costing almost as much as the transfer fee, I'd get one to just try it out. If you don't like it, re-gift it to a family member or something. Just an opinion of someone who owns both aluminum and poly lowers. Let me know if you have specific questions.
^ Honestly, I don't see any real pros in this list above.
*Corrosion. Polymer CAN be corroded. In addition to UV degradation, there are any number of chemicals and solvents that can corrode polymer.
*Fit. Upper-to-lower fit is a non-issue on the AR platform. If it's in spec, it fits.
*Trimming? If you have to trim something, it's not in spec. See above.
*Lifetime warranty. So the poster cracked a magwell installing/removing a barrel nut? I've NEVER seen that happen to a forged lower when properly installing/removing a barrel or barrel nut. But, then again, if the lower was still attached to the upper, the barrel nut was not being properly installed/removed. This was user error and not a warranty issue.
Polymer AR lowers may be a few dollars cheaper (though I saw Anderson lowers for under $35 on Black Friday). That's about it. Everything else is cons. I just have to call it like I see it.
.
*Corrosion. Polymer CAN be corroded. In addition to UV degradation, there are any number of chemicals and solvents that can corrode polymer.
*Fit. Upper-to-lower fit is a non-issue on the AR platform. If it's in spec, it fits.
*Trimming? If you have to trim something, it's not in spec. See above.
*Lifetime warranty. So the poster cracked a magwell installing/removing a barrel nut? I've NEVER seen that happen to a forged lower when properly installing/removing a barrel or barrel nut. But, then again, if the lower was still attached to the upper, the barrel nut was not being properly installed/removed. This was user error and not a warranty issue.
Polymer AR lowers may be a few dollars cheaper (though I saw Anderson lowers for under $35 on Black Friday). That's about it. Everything else is cons. I just have to call it like I see it.
.
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The GWACs armory lower is the only one worthwhile. This is the Cav Arms lower. It was bought out when Cavalry Arms went under.
It's nice and light, strong and well made. The only drawback is it has a fixed A1 length stock and you can't change the pistol grip.
http://www.gwacsarmory.com/cav-15-mkii-ar15-polymer-stripped-lower-receiver-black-ar-15/
https://www.youtube.com/watch?v=GrY-w_C-GAQ
It's nice and light, strong and well made. The only drawback is it has a fixed A1 length stock and you can't change the pistol grip.
http://www.gwacsarmory.com/cav-15-mkii-ar15-polymer-stripped-lower-receiver-black-ar-15/
https://www.youtube.com/watch?v=GrY-w_C-GAQ
I've bought and made a few of the Polymer 80 lowers. I have used them on 2 5.56 and a 7.62x39 upper. All fit tight without any rattle. Doesn't have more than 500 rounds through them yet but have no issues. Not saying they are better than metal lowers but they they work. They are what they are, for a home build they are easy to machine without buying a bunch of tools. The Polymer 80 ones come with a one time use jig and bits.
TrueBlue711
New member
Honestly, I don't see any real pros in this list above.
Yeah, the list isn't exactly a strong case for poly lowers. And I'm not trying to say poly lowers are better than aluminum lowers. If I was building one AR, I would choose aluminum. I'm just trying to say that poly lowers aren't as bad as they once were or as bad as the internet gossip is saying and they're worth at least a look. I'm basing this off of personal experiences having & using both vs. an opinion from those who never even touched one.
*Lifetime warranty. So the poster cracked a magwell installing/removing a barrel nut? I've NEVER seen that happen to a forged lower when properly installing/removing a barrel or barrel nut. But, then again, if the lower was still attached to the upper, the barrel nut was not being properly installed/removed. This was user error and not a warranty issue.
Agreed, an aluminum lower wouldn't have cracked under these same conditions. Yes, the barrel nut was improperly installed by whoever the previous owner was and I was improperly uninstalling it (I only had a magwell vice block, no an upper reciever vice block). Point here was that no matter what happens to lower (user error or not), the TN Arms will replace it free of charge.
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FrankenMauser
New member
I have run a couple brands.
Most prolific and notable were the TAC (TN Arms Corp) lowers.
I was, initially, a fan.
But I soon grew tired of fighting them so much - and that included Gen I, II, and III.
Just some of the issues:
1. Lots of cleanup. They were far from finished lowers. I had to do a lot of clean up on all of them.
2. At least through Gen III, the pocket in the lower for the takedown pin lug on the upper was too wide. It allowed for a misalignment of the receivers which, in turn, allowed the carrier to strike (or completely bind up on) the receiver extension. ALL of mine had to have shims installed to correct that issue.
3. They warp. Leave an assembled rifle with a heavy upper standing on the butt stock for six months, and you'll find the receiver sides bowed. Leave one of the lowers sitting around on its own for six months, and you'll find the thing twisted, bowed, and requiring a little extra muscle to mate it to an upper - including having to spread the hinge pin lugs on mine - and then a magazine or mag well vise block may need to be forcefully inserted into the bowed mag well, to let it 'stretch' for a while.
4. Parts don't fit like they're supposed to. Trigger and hammer pin holes were often the wrong size. Takedown and hinge pin holes had to be reamed. The curved transition from the top of the 'deck' to the buffer tower/boss had to be reshaped just to install an upper. Magazine release holes had to be hogged out with a rotary burr and chisels. Pistol grip webs/bosses were oversized and had to be trimmed (not the easiest job, since there's so little polymer holding that brass insert in place). Selector switch detent holes were oversized, and the pocket too deep under the selector - sometimes allowing the detent pin to rotate right out of the hole while operating the selector, but nearly always making operation stiff and vague at the same time.
Are the Gen IVs and Vs better?
I don't know, and I'm not going to find out.
I have two TAC lowers left here. One is used as a backup for rifle uppers. The other is my backup 'pistol' lower. They don't actually get used. It's more a matter of theory...
All others were sold, given away, or destroyed.
Most prolific and notable were the TAC (TN Arms Corp) lowers.
I was, initially, a fan.
But I soon grew tired of fighting them so much - and that included Gen I, II, and III.
Just some of the issues:
1. Lots of cleanup. They were far from finished lowers. I had to do a lot of clean up on all of them.
2. At least through Gen III, the pocket in the lower for the takedown pin lug on the upper was too wide. It allowed for a misalignment of the receivers which, in turn, allowed the carrier to strike (or completely bind up on) the receiver extension. ALL of mine had to have shims installed to correct that issue.
3. They warp. Leave an assembled rifle with a heavy upper standing on the butt stock for six months, and you'll find the receiver sides bowed. Leave one of the lowers sitting around on its own for six months, and you'll find the thing twisted, bowed, and requiring a little extra muscle to mate it to an upper - including having to spread the hinge pin lugs on mine - and then a magazine or mag well vise block may need to be forcefully inserted into the bowed mag well, to let it 'stretch' for a while.
4. Parts don't fit like they're supposed to. Trigger and hammer pin holes were often the wrong size. Takedown and hinge pin holes had to be reamed. The curved transition from the top of the 'deck' to the buffer tower/boss had to be reshaped just to install an upper. Magazine release holes had to be hogged out with a rotary burr and chisels. Pistol grip webs/bosses were oversized and had to be trimmed (not the easiest job, since there's so little polymer holding that brass insert in place). Selector switch detent holes were oversized, and the pocket too deep under the selector - sometimes allowing the detent pin to rotate right out of the hole while operating the selector, but nearly always making operation stiff and vague at the same time.
Are the Gen IVs and Vs better?
I don't know, and I'm not going to find out.
I have two TAC lowers left here. One is used as a backup for rifle uppers. The other is my backup 'pistol' lower. They don't actually get used. It's more a matter of theory...
All others were sold, given away, or destroyed.
Crankylove
New member
I’ve got two, both Tennessee Arms, one AR15, one AR10 style.
The AR15 style was built two years ago, and has had zero problems. All parts fit with no issues (original owner may have cleaned up both lowers before I got them, so maybe they were good to go from the factory, maybe not), upper to lower fit is as good as my ‘73 SP1. Comparing my rifle to similar rifles in the family, the weight difference is noticeable, but, it’s not enough to honestly make a difference. Barrel length and contour, handgaurd, optics, etc are much more noticeable than the difference between a poly or aluminum lower.
The AR10 style is being built into a .358 Winchester. So far, it’s just an assembled lower, but haven’t had any issues yet. I’m not sure how it will hold up to that cartridge, but I’m gonna give it a whirl.
I received them both as gifts, and between the lower and other components that came from two of my brothers left over parts boxes, I’m into that AR15 $85 (barrel was another gift, bought the BCG on sale for $65). Plan was/is to build it and shoot it until the lower had issues, then replace it with an aluminum lower. But, it’s still going fine with the poly lower, so I’m in no rush to pick up another lower.
I would prefer aluminum, and would not have bought the poly lowers myself, but the price was right, so I’ll run them until they give me a reason not to.
The AR15 style was built two years ago, and has had zero problems. All parts fit with no issues (original owner may have cleaned up both lowers before I got them, so maybe they were good to go from the factory, maybe not), upper to lower fit is as good as my ‘73 SP1. Comparing my rifle to similar rifles in the family, the weight difference is noticeable, but, it’s not enough to honestly make a difference. Barrel length and contour, handgaurd, optics, etc are much more noticeable than the difference between a poly or aluminum lower.
The AR10 style is being built into a .358 Winchester. So far, it’s just an assembled lower, but haven’t had any issues yet. I’m not sure how it will hold up to that cartridge, but I’m gonna give it a whirl.
I received them both as gifts, and between the lower and other components that came from two of my brothers left over parts boxes, I’m into that AR15 $85 (barrel was another gift, bought the BCG on sale for $65). Plan was/is to build it and shoot it until the lower had issues, then replace it with an aluminum lower. But, it’s still going fine with the poly lower, so I’m in no rush to pick up another lower.
I would prefer aluminum, and would not have bought the poly lowers myself, but the price was right, so I’ll run them until they give me a reason not to.
I had a bunch of the "Plum Crazy" polymer lowers and all worked well enough. Still have one that's been used on a 22lr upper, a 5.45x39, and a .223-all satisfactorily. One buyer abused his like a torture test. Bullet hose left on the pickup dash year-round and still no problems.
turtlehead
New member
I had a TAC a couple years ago. Tight fit to my upper. Cool logo. Looked good. Light weight. Floppy bolt catch. Really bothered me.
The AR was not designed with a polymer lower in mind. Aero lowers are so nice and so cheap, why not get the real thing? They're going for $49.99 near me.
The AR was not designed with a polymer lower in mind. Aero lowers are so nice and so cheap, why not get the real thing? They're going for $49.99 near me.
marine6680
New member
Modern polymers are amazing substances. They can be very strong for the weight.
I have seen polymer pieces survive, where aluminum would be mangled, and even steel would bend at least some.
The problem with polymers is they typically come in two varieties... (At least when it comes to polymers suitable for structure components like a receiver)
Stiff, hard and strong.
Or
Strong yet pliable... Or at least somewhat flexible.
You can mix the properties a bit using reinforcement methods like fiber fill... But it's not perfect for all cases.
The slightly flexible polymers can be beaten against a rock and not deform or crack... not that you can't push them too far, you can, and they will bend a bit... But the right formulation would handle any likely hard use scenarios... But in a dynamic system like a rifle, the flexibility would cause issues.
The more stiff polymers can handle a lot of abuse, but when you cross the limit, they crack. They work well in a rifle during firing, but you will eventually have issues with cracking in stress areas.
All that said... An AR receiver is not very conducive to polymer construction.
Areas like the transition to the threaded buffer tube mounting point, the mag well, and the pivot pin tabs... Those are a few of the vulnerable places on a polymer AR receiver.
You would need some reinforcement in those areas, and some makers do, but I don't think they go far enough... Simple inserts and side plates are not enough in my view.
For a poly AR receiver to work... You would need the rear buffer tube mounting point to have a metal reinforcement, that also extends down into the receiver body. Then both sides, the front of the mag well, and the pivot pin mounting tabs, all need reinforcement as well... Plus an insert for the grip screw.
Ideally a thin box of steel, with the buffer tube reinforcement, and pivot pin reinforcement attached... Would stabilize the polymer and prevent cracking, and eliminating most of the weak points.
Weight savings would be fairly small, so not really worth it in my opinion... Not when I can spend $20 more for a good Aero or PSA lower.
That poly lower that has the stock and grip built into it, that design is pretty solid... But it does have its own negatives too.
I have seen polymer pieces survive, where aluminum would be mangled, and even steel would bend at least some.
The problem with polymers is they typically come in two varieties... (At least when it comes to polymers suitable for structure components like a receiver)
Stiff, hard and strong.
Or
Strong yet pliable... Or at least somewhat flexible.
You can mix the properties a bit using reinforcement methods like fiber fill... But it's not perfect for all cases.
The slightly flexible polymers can be beaten against a rock and not deform or crack... not that you can't push them too far, you can, and they will bend a bit... But the right formulation would handle any likely hard use scenarios... But in a dynamic system like a rifle, the flexibility would cause issues.
The more stiff polymers can handle a lot of abuse, but when you cross the limit, they crack. They work well in a rifle during firing, but you will eventually have issues with cracking in stress areas.
All that said... An AR receiver is not very conducive to polymer construction.
Areas like the transition to the threaded buffer tube mounting point, the mag well, and the pivot pin tabs... Those are a few of the vulnerable places on a polymer AR receiver.
You would need some reinforcement in those areas, and some makers do, but I don't think they go far enough... Simple inserts and side plates are not enough in my view.
For a poly AR receiver to work... You would need the rear buffer tube mounting point to have a metal reinforcement, that also extends down into the receiver body. Then both sides, the front of the mag well, and the pivot pin mounting tabs, all need reinforcement as well... Plus an insert for the grip screw.
Ideally a thin box of steel, with the buffer tube reinforcement, and pivot pin reinforcement attached... Would stabilize the polymer and prevent cracking, and eliminating most of the weak points.
Weight savings would be fairly small, so not really worth it in my opinion... Not when I can spend $20 more for a good Aero or PSA lower.
That poly lower that has the stock and grip built into it, that design is pretty solid... But it does have its own negatives too.
Just say no to polymer LR, no up side in any aspect/regard.
http://palmettostatearmory.com/psa-ar-15-lower-safe-fire-1728.html
$39.99 for a nice lower.
http://palmettostatearmory.com/psa-ar-15-lower-safe-fire-1728.html
$39.99 for a nice lower.
InRange has run their 'What Would Stoner Do?' ARs with the polymer lowers HARD, including matches, without problem. Karl also has a lower that was shot repeatedly during a torture test, but has yet to fail to function:
https://www.youtube.com/watch?v=xjhvi8c0MF4
Using the same lower in competition:
https://www.youtube.com/watch?v=CoLp3AWeXOM
https://www.youtube.com/watch?v=xjhvi8c0MF4
Using the same lower in competition:
https://www.youtube.com/watch?v=CoLp3AWeXOM
Every so often Anderson sells lowers for 29$.
There used to be a PRO for polymer lowers when aluminum lowers could not be found at a reasonable price. Now that they are almost giving them away, I see no point in polymer. Not afraid of polymer at all, my only beef is they should cost $10 or less in my mind.
There used to be a PRO for polymer lowers when aluminum lowers could not be found at a reasonable price. Now that they are almost giving them away, I see no point in polymer. Not afraid of polymer at all, my only beef is they should cost $10 or less in my mind.