View Full Version : Make You Think Twice Before Buying a Polymer Lower Receiver
rooster2412
12-31-21, 20:23
They are inexpensive for many reasons, champane tastes on a beer budget and then this happens....
https://images2.imgbox.com/84/18/LBb2Aj0e_o.jpg
Inkslinger
12-31-21, 20:34
I agree. But know this, it can happen to aluminum lowers of questionable quality as well. I had a Hesse Arms in the late 90’s (clearly the questionable quality I was referring to) that broke in the exact same manner. My guess is now a days even with low quality aluminum lowers, it probably happens much less frequently than with polymer lowers.
If it won't buff out like george said, superglue it. I thought plastic lowers were only good for .22 LR's or something like that.
titsonritz
12-31-21, 21:05
If it does not have an integral stock like the KE Arms KP-15 don't bother, it is a waste of money.
Is there supposed to be a picture?
titsonritz
12-31-21, 21:17
Is there supposed to be a picture?
Yes, of a US Arms Patriot-15 snapped in the usual spot.
m1a_scoutguy
12-31-21, 21:18
Come on guys,,JB Weld,,Super Glue is soooo old school !!! :D:D
If it does have an integral stock like the KE Arms KP-15 don't bother, it is a waste of money.
"does" or "doesn't"?
I thought the KE Arms w/integral stock was GTG.
titsonritz
12-31-21, 21:37
"does" or "doesn't"?
I thought the KE Arms w/integral stock was GTG.
Does not sorry, fixed.
Come on guys,,JB Weld,,Super Glue is soooo old school !!! :D:D
Yeah, you're right, JB Weld, that will most definitely fix it. I use it to fix my engine blocks when I throw rods through them. That stuff is amazing.
Nothing I would ever even consider buying.
What’s the story? Did the AR have to be mortared?
defense523
01-01-22, 11:07
Add to the fact that HPR ammo has been discontinued for YEARS and was know to have...1 or 2 QC issues to go with their KBs, and you have a catastrophic failure waiting to happen.
I’ve seen a few iterations of 3D printed lowers. Two that I recall reinforce this area specifically with additional material and/or a hose clamp.
I haven’t seen one complete a multi thousand round run though.
3beansalad
01-01-22, 12:52
Add to the fact that HPR ammo has been discontinued for YEARS and was know to have...1 or 2 QC issues to go with their KBs, and you have a catastrophic failure waiting to happen.I read to say it's possible this photo is old and being used to spread hysteria about polymer gun parts. Thought provoking.
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I read to say it's possible this photo is old and being used to spread hysteria about polymer gun parts. Thought provoking.
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Maybe rooster needs to explain to us how old this photo is and his purpose for throwing it up.
I still wouldn't use a modern plastic receiver for anything other than a 22 LR. And probably not even for that. There are cheap aluminum lowers available.
Only polymer one worth buying is the KE Arms.
Maybe the OP should have used one of those $700 lowers he’s trying to peddle instead?
I see no reason to roll the dice on Polymer when you can buy any number of well machined, in tolerance aluminum stripped lowers equal to or less than the cost of this trash.
bulletproofwelding_1
01-01-22, 14:05
I would tell you to only good brands I personally I stay away for Anderson and other new brands that have came to market up over the last few year most of them are garbage.
Never thought once about a poly AR.
3beansalad
01-01-22, 17:20
My very first AR was a polymer lower. It's still in the safe and functions properly. When I purchased the New Frontier polymer I have, the panic was high and I felt like having an AR was better than not, no matter the materials. Everything since, all aluminum. I don't plan on going back for another polymer, but printing one is an attractive option.
I firmly believe most failures can be traced to an over torqued castle nut. When 20 ft lbs is spec'd, hand tight can easily exceed that. I don't think polymer lowers are perfect, but I do believe when assembled properly, and inspected regularly, they shouldn't fail fantastically at the range. And therefore photos such as this are given more credit than they deserve. Possibly as a form of advertising/ endorsing something else. Of course, we all know what opinions are like.
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my only question is why when you can buy a standard lower for $50 give or take. $10 or so does not warrant enough of a difference to buy a poly lower regardless of function.
Poly lowers are what $30? You can buy Anderson at $40-50 so why is how I view it.
3beansalad
01-01-22, 19:07
my only question is why when you can buy a standard lower for $50 give or take. $10 or so does not warrant enough of a difference to buy a poly lower regardless of function.
For me, in the days/ weeks following Obama's election, it was due to availability. I admit I bought because I was concerned about potential legislation. In retrospect, I could have easily waited for an aluminum lower.
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My very first AR was a polymer lower. It's still in the safe and functions properly. When I purchased the New Frontier polymer I have, the panic was high and I felt like having an AR was better than not, no matter the materials. Everything since, all aluminum. I don't plan on going back for another polymer, but printing one is an attractive option.
I firmly believe most failures can be traced to an over torqued castle nut. When 20 ft lbs is spec'd, hand tight can easily exceed that. I don't think polymer lowers are perfect, but I do believe when assembled properly, and inspected regularly, they shouldn't fail fantastically at the range. And therefore photos such as this are given more credit than they deserve. Possibly as a form of advertising/ endorsing something else. Of course, we all know what opinions are like.
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Hand tight on the castle nut doesn't seem like a good long term reliability situation.
For me, in the days/ weeks following Obama's election, it was due to availability. I admit I bought because I was concerned about potential legislation. In retrospect, I could have easily waited for an aluminum lower.
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I get that, you were not alone there. We live and learn, I keep a few spare......ALWAYS! LOL
3beansalad
01-01-22, 19:19
Hand tight on the castle nut doesn't seem like a good long term reliability situation.I believe you misread my words, but I don't disagree. Manufacturers have specs for a reason though.
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I believe you misread my words, but I don't disagree. Manufacturers have specs for a reason though.
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I was going off the first two sentences of your second paragraph. Is 20 ft/lbs a plastic receiver spec? I thought for aluminum receivers it was something like 35-40 ft/lbs.
3beansalad
01-01-22, 19:49
I was going off the first two sentences of your second paragraph. Is 20 ft/lbs a plastic receiver spec? I thought for aluminum receivers it was something like 35-40 ft/lbs.I'm sure every manufacturer is different but for the New Frontier lower I found on their current site, yes. 20 ft lbs max for the castle nut.
https://www.newfrontierarmory.com/product/lw-4-stripped-carbon-fiber-lower/
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If people do have some interest in polymer AR lowers, this is a nice Gun Jesus video on the history. If that gets your interest, the InRange WWSD used one of these type of lowers, and had a good deal of info on them throughout that project.
https://youtu.be/RFxNvi7920c
Spark notes version… if a polymer lower based off a traditional AR lower is going to break, it will happen between the buffer tube threads and the pistol grip. Not a lot of strength there, and sort of where the “abuse” is going to focus on. Aluminum has the strength to not break under most common setups, but polymer is different. The one piece stock/grip/lower… is what solves that (Colt noticed that when they tried).
I tried the TN Arms lowers years back, and sent them all back for a refund (none were in spec, and I got tired of messing with them). But the KE Arms one is good to go. I got one pretty cheap, as I have a FFL-03 that is linked to my Brownell’s account. Built it with a lightweight 16” upper, and after adding a sling, light, and red dot… it came in the 6 pound realm. That is good enough for me in regards to a backup AR.
If we are going to consider rimfire, the M&P 15/22 is awesome. I have the braced pistol, and cannot wait to get my suppressors out of jail just for use with that pistol. A 3.5 pound pistol is nice when you are in this configuration. And if AFT decides braces are stocks… I’d SBR that with zero hesitation.
I'm sure every manufacturer is different but for the New Frontier lower I found on their current site, yes. 20 ft lbs max for the castle nut.
https://www.newfrontierarmory.com/product/lw-4-stripped-carbon-fiber-lower/
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they made the best x39 barrels out there, wish they still did
For me, in the days/ weeks following Obama's election, it was due to availability. I admit I bought because I was concerned about potential legislation. In retrospect, I could have easily waited for an aluminum lower.
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Indeed. In '08, I wound up with an SU16C. While not a 'fighting' rifle, it has run flawlessly through thousands of rounds. In '16, I did get an AR.
ViniVidivici
01-01-22, 22:36
Way I see it.....polymer pistol frames came out years ago....now almost every major manufacturer makes a polymer framed pistol.
Polymer AR lowers have, as a concept, been around for years.....and almost NO manufacturer makes them.
Clue.
They are inexpensive for many reasons, champane tastes on a beer budget and then this happens....
https://images2.imgbox.com/84/18/LBb2Aj0e_o.jpg
Cheap is cheap. Have a high end polymer has not snapped yet. Same people who cried for decades about polymer pistols are in the never polymer lowers theater. It's cheaper to buy a forged aluminum lower than a high end polymer lower so unless you have a weight specific reason I would say stay away from cheap polymer lowers. And in the end anything can break.
Cheap is cheap. Have a high end polymer has not snapped yet. Same people who cried for decades about polymer pistols are in the never polymer lowers theater. It's cheaper to buy a forged aluminum lower than a high end polymer lower so unless you have a weight specific reason I would say stay away from cheap polymer lowers. And in the end anything can break.
Oh brother! You do realize that there's a world of difference between a pistol frame and an AR lower, right? Especially a pistol frame designed from the ground up to be polymer, versus an AR lower receiver designed to be made from aluminum. Ever notice how pistol frames don't have large holes where take down pins go through? Notice how plastic AR lowers almost always break at the take down pin?
ETA:
https://upload.wikimedia.org/wikipedia/commons/8/89/Receiver12.1.png
reaper5.56
01-02-22, 08:22
I remember the ffl I as using at the time getting many dozens of those" plum crazy lowers I think they were called in and trying to sell me on them
3beansalad
01-02-22, 08:27
Oh brother!
ETA:
https://upload.wikimedia.org/wikipedia/commons/8/89/Receiver12.1.png
I've never seen this image before, but it also reaffirms my thought process on the breakage in the OPs photo. Something caused that. Impact? improper assembly? We'll never know for sure.
The BCG moves as close to straight back as anything, and should never "bottom out" in the buffer tube. Muzzle flip, or rise, is a real thing but the design is intended to have those forces absorbed by the buffer spring. And wouldn't apply to the lower reciever in the direction depicted. What I'm trying to say is that nothing should do what is shown in the wiki photo.
Of course aluminum is far more resistant to abuse and should be your first choice. But something causes the breakage of polymer lowers, and I have to believe it can be avoided.
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I've never seen this image before, but it also reaffirms my thought process on the breakage in the OPs photo. Something caused that. Impact? improper assembly? We'll never know for sure.
The BCG moves as close to straight back as anything, and should never "bottom out" in the buffer tube. Muzzle flip, or rise, is a real thing but the design is intended to have those forces absorbed by the buffer spring. And wouldn't apply to the lower reciever in the direction depicted. What I'm trying to say is that nothing should do what is shown in the wiki photo.
Of course aluminum is far more resistant to abuse and should be your first choice. But something causes the breakage of polymer lowers, and I have to believe it can be avoided.
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The buffer has bumper on it to soften the impact of it hitting the back of the receiver extension because the buffer hits the back of the receiver extension.
A few years ago, a trainer used a polymer lower on the AR used in his classes. After a couple three thousand rounds or so, the lower broke in the usual place. He didn’t put it through any abuse, just shot it. It broke just from a heavy firing schedule.
The only way to avoid it is to not shoot much.
Wonder if a constant recoil system would over come the issue?
KE polymer lower doing full-auto mag dumps. Starting at about 8:00, there are also pushups, a run-over, pullups AND buttstrokes against a 4x4 post.
https://youtu.be/YQ451lbKW0o
Inkslinger
01-02-22, 16:51
KE polymer lower doing full-auto mag dumps. Starting at about 8:00, there are also pushups, a run-over, pullups AND buttstrokes against a 4x4 post.
https://youtu.be/YQ451lbKW0o
I’m sure they’re wonderful, and you are free to spend your money as you see fit. I posted earlier that I had an aluminum receiver break in the exact same manner. In 25 years since and multiple aluminum lowers, I have not experienced this again. I see no advantage worth rolling the dice with a polymer receiver.
I’m sure they’re wonderful, and you are free to spend your money as you see fit. I posted earlier that I had an aluminum receiver break in the exact same manner. In 25 years since and multiple aluminum lowers, I have not experienced this again. I see no advantage worth rolling the dice with a polymer receiver.
I’m not in a hurry to buy a polymer lower either. 🙂
During the peak of one of the Obama scares one of my buddies got all "MUST HAVE" over some no name 5.7upper and payed some rediculous amount for it. To maintain the continuity of retardation he grabbed an ATI polymer lower, the only lower he could find.
He brought this contraption over to my place and we pieced it together with bushmaster take off parts. It had a card in the box specifically warning against using a non mil-spec buffer tube. Advising him that the bushy non mil-spec tube was all I had to spare, he wanted to press on. What difference could it make?
The lower lasted 9rds before it broke as shown above.
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titsonritz
01-04-22, 23:52
Possibly the only legit use I've seen for one of these types of lowers (3:25 min)...
https://www.youtube.com/watch?v=ieHCpBj5Djs
What was the approximate round count of the rifle when that occured?
What was the approximate round count of the rifle when that occured?
If you're asking me, I don't recall. It was some thousand. The guy said it was worth what he paid for it. This was back in the day when polymer lowers were no more than $30. He looked at it like he'd worn out a barrel. He said "No big deal. I'll just replace it and continue shooting."
Maybe the OP should have used one of those $700 lowers he’s trying to peddle instead?
I see no reason to roll the dice on Polymer when you can buy any number of well machined, in tolerance aluminum stripped lowers equal to or less than the cost of this trash.
You’ve made a typo, sir. His lowers are $1000 and $1600.
And I echo the sentiment on polymer. Perhaps the KE Arms one is acceptable.
I can't remember how long ago it's been because time flies, but this happened when I was shooting with the local sheriff's department during their quals a few years ago. The deputy simply racked the charging handle and this exact thing happened. He wasn't the kind of deputy that regularly shot either. In fact, I'd place a five dollar bet it was the first time he'd attempted to charge the rifle. The whole sheriff's department was issued rifles built on this brand of lower and there were many problems. I can't remember what the rules are on posting manufacturer's names, so I won't do it.
Needless to say, over the years most have purchased and qualed with their own ARs. I think there may be a few of the polymers floating around still.
KE polymer lower doing full-auto mag dumps. Starting at about 8:00, there are also pushups, a run-over, pullups AND buttstrokes against a 4x4 post.
https://youtu.be/YQ451lbKW0o
I've no desire to own one nor will I however, this lower did pretty well. I do believe with advances in polymers etc, they may be viable in the future as we already have poly products stronger than steel with a 1/10 the weight. The real issue I see is the environmental impacts for instance, how will they do in artic conditions? impressive regardless but still only for a .22:)
I've no desire to own one nor will I however, this lower did pretty well. I do believe with advances in polymers etc, they may be viable in the future as we already have poly products stronger than steel with a 1/10 the weight. The real issue I see is the environmental impacts for instance, how will they do in artic conditions? impressive regardless but still only for a .22:)
Agreed, this is for the 'nice to have something different' crowd, but there's enough of those to make this relatively successful. And there's no telling how the tech will continue to evolve.
I owned two complete poly lowers, a Plum Crazy and a New Frontier. Back when a Rock River Arms complete lower was $250, these were $99. All parts including the FCG were plastic except for the bolt catch.
The hammer on the New Frontier started to disintegrate, causing double taps. Later one of the detent pins for the takedown pins snapped off. Got rid of both eventually.
Now the original pic looks like someone either fell on it or tried to mortar it.
For range use, they’re fine. But aluminum isn’t that much more these days.
I picked up a few KE Arms lowers one set up with a light weight 20 in barrel the other with a light weight 18 in mid but as many here I don't just have one AR to go with. If it fails I'm out less than what I normally expend in ammo on a range trip. Then I've still got a good lower parts group and upper, I might have a few stripped lowers waiting for parts too. I wouldn't recommend one for anything larger than 5.56 but I've been using one with 20 in barrel and suppressor since they were available, not ran hard but suppressed. I wouldn't recommend any other polymer lower heck a few years ago someone made a lower out of wood that works. Now that is a failure in the making. Farm Crafter has made one from cast beer cans and a AR-10 from brass lower both are sand castings. Now my oh S### out the door would be my SBR or 6920. Now I wouldn't issue or equip a unit to go to battle with them yet, but I do think there is potential in polymer for rifles in AR-15 platform. The AR-10, AR-15 started with that "new fangled" aluminum and plastic in 1950-60s look what that has done to modern warfare alone. The lower may end up looking a lot different than what it does now. Yes most if not all before now have been hot garbage.
Food for though.
I have a Tegra lower as a base for an A2 carbine, and it's holding up well. It's a range carbine I built to train my kids. Tegra has a lifetime on it: I spoke with them prior to purchase and they are fascinating folks. I like innovative products but I wouldn't use it as a defensive carbine. I have plenty of lowers I could swap out with it if it ever breaks. It's pretty attractive and light.
I picked up a few KE Arms lowers one set up with a light weight 20 in barrel the other with a light weight 18 in mid but as many here I don't just have one AR to go with. If it fails I'm out less than what I normally expend in ammo on a range trip. Then I've still got a good lower parts group and upper, I might have a few stripped lowers waiting for parts too. I wouldn't recommend one for anything larger than 5.56 but I've been using one with 20 in barrel and suppressor since they were available, not ran hard but suppressed. I wouldn't recommend any other polymer lower heck a few years ago someone made a lower out of wood that works. Now that is a failure in the making. Farm Crafter has made one from cast beer cans and a AR-10 from brass lower both are sand castings. Now my oh S### out the door would be my SBR or 6920. Now I wouldn't issue or equip a unit to go to battle with them yet, but I do think there is potential in polymer for rifles in AR-15 platform. The AR-10, AR-15 started with that "new fangled" aluminum and plastic in 1950-60s look what that has done to modern warfare alone. The lower may end up looking a lot different than what it does now. Yes most if not all before now have been hot garbage.
Food for though.
actually, I'm expecting to see more of the 'pressed wood' design as it's stronger than steel at 1/10th the weight. This type of wood is now being used in aviation and boating to great success as the barometric stress is less on the wood too.
people laughed at the mosquito too and you are right on where the overall platform has come from in the 50s and 60s
good post
My father is a pilot and we attend events each year prior to the virus hysteria, and I have come across a bunch of X models and I am always interested to see the materials they are using. I have also been working with woods for years and have learned a great deal about composites, joints, and bonding adhesives etc. They still make car frames out of woods, and fibers. I asked an X model pilot about kevlar and he immediately redirected me to carbon fiber. Nature has evolved materials far stronger than steel: take the spiders web. Those who analyze these natural materials and use AI to model them, will be the pioneers of the future in materials engineering.
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