Polymer AR lowers

Bill DeShivs · February 12, 2017, 12:24 AM

Even though I have a couple of AR 15s, I'm not much of an AR guy.
I'm thinking about buying an 80% receiver to replace one of my AR receivers.
While I have the equipment to mill the aluminum receiver, I have been toying with the idea of getting a polymer lower.
Am I insane? Wait- don't answer that!

Is this a bad idea?

turtlehead · February 12, 2017, 12:27 AM

Yep.

FrankenMauser · February 12, 2017, 12:55 AM

I have had something like eight 'finished' polymer lowers, and another pair of "80%" polymer lowers that I finished myself.

Only one, maybe two of the 'finished' polymer lowers remains in my possession (one "rifle", maybe one "pistol", I think). And both of the 80% lowers have been relegated to the wall of shame.

Too much shrinkage, too much warpage, and too many out-of-spec areas in all of them.

They all worked, but none worked well. All had problems, irritations, and reliability issues. And all required work to install almost every single part, and then get them running -- even the 'finished' lowers.

The eighty-percenters (Polymer80), to get closer to the actual question, were just garbage. The list of problems was a mile long, but the biggest issue was that the type of material used for the lowers was extremely prone to chipping or breaking out while milling or drilling, which resulted in some very obnoxious and seemingly-unavoidable damage.
Mine were early production, so they may have worked some bugs out by now; but my experience was less than stellar.

When I need another lower, now.... I buy an Aero Precision.

TruthTellers · February 12, 2017, 01:01 AM

Don't use polymer, it's not built to last.

There was a company at SHOT last month that debuted Magnesium lowers that are much lower in weight to standard aluminum ones. They impressed me so much that I may just buy one (or two) of their lowers and build my first AR. If I can make an AR with a medium diameter 1:7 twist 20 inch barrel and make it no more than 6.5 lbs, it's a gotta have.

Then, if I can make a 16 inch skinny pencil barrel with a red dot sight and keep the weight to 5 lbs or less, again, gotta have it.

peggysue · February 12, 2017, 05:52 AM

Everyone needs a ghost gun or 2. It is fun to transform a 80% to 100%. Sadly a finished lower is cheaper now days.

O4L · February 12, 2017, 11:48 AM

Friends don't let friends buy polymer lowers.

I don't see the point. There are very usable finished forged aluminum lowers to be found for $50 and less.

If the point is to have a lower without a paper trail, just buy one from an individual. Mission accomplished.

Dunsouth · February 12, 2017, 11:56 AM

TruthTellers,
What magnesium lower are you talking about? I recently did a build with the purpose of having a sub 7lb big woods rifle. The idea being that I can shoot both a 300 ACC upper and a 458 Socom upper on the same lightweight lower. I use a Mag Tactical magnesium alloy lower and came in easily under 7lbs scoped with a mag (no ammo). I could go lighter as my goal was simply under 7lbs scoped and I did not push some areas as far as I could have. Although I have been told a battelink minimalist stock is in transit for me to test with the 458 Socom. This will cut the weight and get closer to 6lbs. as it is almost half the weight of the Magpul FCS with QD mount and the longer spacer.

Mag Tactical is no longer producing these lowers and have been purchased by Fostech. If there is another maker I would be very interested in them for future builds. I would also love to see Fostech make these as I am in Indiana as are they.

turtlehead · February 12, 2017, 12:00 PM

I even bought a plastic FCG just to see if it worked. Fired about 200 rounds with it without issue. Then I sold it along with 2 polymer lowers.

What's the point if you're always thinking "how long until it breaks"? There are so many good 7075 receivers out there. Prices are great.

Bill DeShivs · February 12, 2017, 05:06 PM

I have a spare aluminum receiver.
Just thought I might finish one. If I do, it will not be polymer.
Thanks!

TruthTellers · February 13, 2017, 12:58 AM

Dunsouth, I do not remember what the name of the company was. I saw it on youtube, believe it was Jeff Quinn and Gunblastdotcom that I saw the lowers on. They may have been Fostech.

Mobuck · February 13, 2017, 07:23 AM

I've elected to forego the 80% lower fad but I do have a couple of non-metallic lowers.
Plum Crazy is the logo and the only thing I've found to complain about is the tight fit of the rear lug. Got several of them when I still had an FFL and sold all but 2. Ran one on the 5.45 for years w/o issue and the other hosted a 22lr upper until I sold that. I did replace the plastic FCG as I began to distrust the safety of such flimsy material.
My thoughts are: if you need a spear, prybar,or club, find such and use them rather than your rifle. Only the military uses their primary weapon for these things. Don't drive your vehicle over your AR and you most likely won't break it.

Fishbed77 · February 13, 2017, 11:25 AM

When quality forged aluminum lowers can be had for $50-$60, polymer lowers don't make much sense.

Dunsouth · February 13, 2017, 01:27 PM

Thanks Truth Tellers. I bet it was the Fostech/Mag Tactical. I haven't heard of any others to date. So far I am a fan. We'll see how it holds up to a 458 upper.

Crankylove · February 15, 2017, 12:11 AM

I have a polymer lower on one of my AR's. It's a Tennessee Arms, and so far has held up ok for the few hundred rounds I've put through it. It's fits my upper well, and I do like the light weight, but polymer would not be my first choice as a lower.

I got a hell of a deal on this one (free) as it was one of Frankenmauser's that I recieved as a birthday present, so I really can't complain (between Frankenmauser and another brother, I was gifted enough left over parts from their builds, along with a barrel they bought for me, that I only had to purchase the BCG to build the rifle, I'm only into my "parts box AR" $85)

I've heard many horror stories of them failing, and while it's working fine right now, it will probably get replaced with an aluminum Aero Precision lower down the road when funds allow.

Ibmikey · February 18, 2017, 09:48 AM

Bill, I have three dozen AR's and one of the most fun to shoot rocks and stuff with is an ATI Omni that I bought as a " shoot to destruction" rifle. It has a poly lower with steel reinforcements and is super accurate with I believe is a D C Machine barrel and came with a cheap red dot, now after thousands of rounds it still chugs along and shoots tiny groups with decent ammo ( which it rarely sees with a diet of reloads).
I do not have a desire for another plastic lower but my Omni is a keeper.

reynolds357 · February 18, 2017, 11:46 PM

Terrible idea.
1. Polymer lowers are not durable.
2. You can get good aluminum finished lowers for $50.

February 12, 2017, 12:24 AM	#1
Bill DeShivs Senior Member Join Date: April 7, 2006 Posts: 10,985	Polymer AR lowers Even though I have a couple of AR 15s, I'm not much of an AR guy. I'm thinking about buying an 80% receiver to replace one of my AR receivers. While I have the equipment to mill the aluminum receiver, I have been toying with the idea of getting a polymer lower. Am I insane? Wait- don't answer that! Is this a bad idea? __________________ Bill DeShivs, Master Cutler www.billdeshivs.com

February 12, 2017, 12:55 AM	#3
FrankenMauser Senior Member Join Date: August 25, 2008 Location: In the valley above the plain Posts: 13,424	I have had something like eight 'finished' polymer lowers, and another pair of "80%" polymer lowers that I finished myself. Only one, maybe two of the 'finished' polymer lowers remains in my possession (one "rifle", maybe one "pistol", I think). And both of the 80% lowers have been relegated to the wall of shame. Too much shrinkage, too much warpage, and too many out-of-spec areas in all of them. They all worked, but none worked well. All had problems, irritations, and reliability issues. And all required work to install almost every single part, and then get them running -- even the 'finished' lowers. The eighty-percenters (Polymer80), to get closer to the actual question, were just garbage. The list of problems was a mile long, but the biggest issue was that the type of material used for the lowers was extremely prone to chipping or breaking out while milling or drilling, which resulted in some very obnoxious and seemingly-unavoidable damage. Mine were early production, so they may have worked some bugs out by now; but my experience was less than stellar. When I need another lower, now.... I buy an Aero Precision. __________________ Don't even try it. It's even worse than the internet would lead you to believe.

February 12, 2017, 05:06 PM	#9
Bill DeShivs Senior Member Join Date: April 7, 2006 Posts: 10,985	I have a spare aluminum receiver. Just thought I might finish one. If I do, it will not be polymer. Thanks! __________________ Bill DeShivs, Master Cutler www.billdeshivs.com

February 15, 2017, 12:11 AM	#14
Crankylove Senior Member Join Date: July 8, 2008 Location: 8B ID Posts: 1,753	I have a polymer lower on one of my AR's. It's a Tennessee Arms, and so far has held up ok for the few hundred rounds I've put through it. It's fits my upper well, and I do like the light weight, but polymer would not be my first choice as a lower. I got a hell of a deal on this one (free) as it was one of Frankenmauser's that I recieved as a birthday present, so I really can't complain (between Frankenmauser and another brother, I was gifted enough left over parts from their builds, along with a barrel they bought for me, that I only had to purchase the BCG to build the rifle, I'm only into my "parts box AR" $85) I've heard many horror stories of them failing, and while it's working fine right now, it will probably get replaced with an aluminum Aero Precision lower down the road when funds allow. __________________ The answer to 1984 is 1776

February 12, 2017, 12:27 AM	#2
turtlehead Senior Member Join Date: October 20, 2015 Location: Phoenix, AZ Posts: 1,203	Yep.

February 12, 2017, 01:01 AM	#4
TruthTellers Senior Member Join Date: October 22, 2016 Posts: 3,887	Don't use polymer, it's not built to last. There was a company at SHOT last month that debuted Magnesium lowers that are much lower in weight to standard aluminum ones. They impressed me so much that I may just buy one (or two) of their lowers and build my first AR. If I can make an AR with a medium diameter 1:7 twist 20 inch barrel and make it no more than 6.5 lbs, it's a gotta have. Then, if I can make a 16 inch skinny pencil barrel with a red dot sight and keep the weight to 5 lbs or less, again, gotta have it.

February 12, 2017, 05:52 AM	#5
peggysue Junior member Join Date: May 20, 2014 Posts: 1,835	Everyone needs a ghost gun or 2. It is fun to transform a 80% to 100%. Sadly a finished lower is cheaper now days.

February 12, 2017, 11:48 AM	#6
O4L Senior Member Join Date: September 16, 2015 Posts: 646	Friends don't let friends buy polymer lowers. I don't see the point. There are very usable finished forged aluminum lowers to be found for $50 and less. If the point is to have a lower without a paper trail, just buy one from an individual. Mission accomplished.

February 12, 2017, 11:56 AM	#7
Dunsouth Junior Member Join Date: February 12, 2017 Posts: 14	TruthTellers, What magnesium lower are you talking about? I recently did a build with the purpose of having a sub 7lb big woods rifle. The idea being that I can shoot both a 300 ACC upper and a 458 Socom upper on the same lightweight lower. I use a Mag Tactical magnesium alloy lower and came in easily under 7lbs scoped with a mag (no ammo). I could go lighter as my goal was simply under 7lbs scoped and I did not push some areas as far as I could have. Although I have been told a battelink minimalist stock is in transit for me to test with the 458 Socom. This will cut the weight and get closer to 6lbs. as it is almost half the weight of the Magpul FCS with QD mount and the longer spacer. Mag Tactical is no longer producing these lowers and have been purchased by Fostech. If there is another maker I would be very interested in them for future builds. I would also love to see Fostech make these as I am in Indiana as are they.

February 12, 2017, 12:00 PM	#8
turtlehead Senior Member Join Date: October 20, 2015 Location: Phoenix, AZ Posts: 1,203	I even bought a plastic FCG just to see if it worked. Fired about 200 rounds with it without issue. Then I sold it along with 2 polymer lowers. What's the point if you're always thinking "how long until it breaks"? There are so many good 7075 receivers out there. Prices are great.

February 13, 2017, 12:58 AM	#10
TruthTellers Senior Member Join Date: October 22, 2016 Posts: 3,887	Dunsouth, I do not remember what the name of the company was. I saw it on youtube, believe it was Jeff Quinn and Gunblastdotcom that I saw the lowers on. They may have been Fostech.

February 13, 2017, 07:23 AM	#11
Mobuck Junior member Join Date: February 2, 2010 Posts: 6,846	I've elected to forego the 80% lower fad but I do have a couple of non-metallic lowers. Plum Crazy is the logo and the only thing I've found to complain about is the tight fit of the rear lug. Got several of them when I still had an FFL and sold all but 2. Ran one on the 5.45 for years w/o issue and the other hosted a 22lr upper until I sold that. I did replace the plastic FCG as I began to distrust the safety of such flimsy material. My thoughts are: if you need a spear, prybar,or club, find such and use them rather than your rifle. Only the military uses their primary weapon for these things. Don't drive your vehicle over your AR and you most likely won't break it.

February 13, 2017, 11:25 AM	#12
Fishbed77 Senior Member Join Date: November 23, 2010 Posts: 4,862	When quality forged aluminum lowers can be had for $50-$60, polymer lowers don't make much sense.

February 13, 2017, 01:27 PM	#13
Dunsouth Junior Member Join Date: February 12, 2017 Posts: 14	Thanks Truth Tellers. I bet it was the Fostech/Mag Tactical. I haven't heard of any others to date. So far I am a fan. We'll see how it holds up to a 458 upper.

February 18, 2017, 09:48 AM	#15
Ibmikey Senior Member Join Date: June 1, 2013 Location: Now relocated to Texas Posts: 2,943	Bill, I have three dozen AR's and one of the most fun to shoot rocks and stuff with is an ATI Omni that I bought as a " shoot to destruction" rifle. It has a poly lower with steel reinforcements and is super accurate with I believe is a D C Machine barrel and came with a cheap red dot, now after thousands of rounds it still chugs along and shoots tiny groups with decent ammo ( which it rarely sees with a diet of reloads). I do not have a desire for another plastic lower but my Omni is a keeper.

February 18, 2017, 11:46 PM	#16
reynolds357 Senior Member Join Date: December 10, 2012 Posts: 6,165	Terrible idea. 1. Polymer lowers are not durable. 2. You can get good aluminum finished lowers for $50.