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Ultra Light ARs: plastic lower receiver?

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koshkin View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote koshkin Quote  Post ReplyReply Direct Link To This Post Topic: Ultra Light ARs: plastic lower receiver?
    Posted: February/07/2018 at 14:31
Folks, anyone with recent experience with plastic AR lowers?

I had completely discarded them in the past, but recently I have been messing with a JMT lower and it feels like it uses a far better material than I recall from the past.

I built it up and it is working very nicely so far, but it hasn't been very long.

Any experience with these on a longer term basis?

I built one up with Geissele SSA-E Trigger and Ace UL stock and I am considering building an ultralight upper to use with it.

The only real weak point I see is where the buffer tube threads into the receiver, which is one of the reasons I used Ace UL stock.  It beefs up that spot a little.  Also, with a rifle length buffer tube and spring/buffer, it is a very soft shooting gun.

Combined with a mid-length or rifle-length gas system, it is quite smooth.

ILya


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Post Options Post Options   Thanks (0) Thanks(0)   Quote RifleDude Quote  Post ReplyReply Direct Link To This Post Posted: February/07/2018 at 15:30
No experience at all with the plastic lowers. I see no reason why they wouldn’t hold up just fine over time, based on a lower’s functional requirements. I elected to go with the lightest alloy lower I could find for my ultralight AR rather than going with polymer, though it’s considerably more expensive. I just feel a gun is more “gunny” whenever the main components are metal wherever feasible. It’s taken me a long time to warm up to polymer framed pistols. Just a hangup of mine.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rancid Coolaid Quote  Post ReplyReply Direct Link To This Post Posted: February/07/2018 at 17:47
I have one, several years old, will look up details on it. I made the mistake of not cutting off a spring and now I cannot remove the trigger without huge modification to the gun.

I like the light weight, I do not attempt mag dumps with it.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote urbaneruralite Quote  Post ReplyReply Direct Link To This Post Posted: February/07/2018 at 20:55
I have used several of the New Frontier. Most use has been on 22lr. Most of the strain there would be from banging around in a dog box, or in the woods at night, more so than shooting. 

The polymer components of the New Frontier have some interesting features. One is that the hammer works well with rimfire, whereas standard FCG parts sometimes need modification. Also, the trigger pull is better than you often find in a mil-spec trigger. They're not good, just good enough to not hate. And, if you're right in the brain, the safety reverses easily with no modification. The diameter of the buffer tube has varied over the years. Double check before buying a better stock.

I have also used them on .223 and 6.5G. Not a lot of use there, but no issues found all the same.

I want to try one from Tennessee Arms Co, but not enough to pay shipping and FFL just yet. If I were building a hard use centerfire, I would take a look at GWACS. 

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Post Options Post Options   Thanks (0) Thanks(0)   Quote koshkin Quote  Post ReplyReply Direct Link To This Post Posted: February/07/2018 at 22:23
I am using a JMT lower that works with regular lower parts, so I do not have to do anything exotic I'm terms of components.

Never heard of GWACS, but I'll check it out. My use is with a 5.56 ultralight upper.

ILya

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Kickboxer Quote  Post ReplyReply Direct Link To This Post Posted: February/08/2018 at 07:25

I got Lori a Wyndham... weighs just over 6lbs.  So far, works great.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote RifleDude Quote  Post ReplyReply Direct Link To This Post Posted: February/08/2018 at 08:37
I was looking at some reviews of the various composite lowers last night. The consensus seems to be that if it does fail, the most common mode of failure is breaking at the narrow portion at the rear below the takedown pin hole. Repeated flexing from the carrier slamming against the buffer gradually forms a stress crack at the bottom of the takedown pin hole and it then spreads until the buffer tube mounting projection breaks off completely.

This may not be an issue at all with the lower you have, but it’s something to keep an eye on.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote koshkin Quote  Post ReplyReply Direct Link To This Post Posted: February/08/2018 at 10:37
I have seen that failure, but it seemed more common on earlier plastic lower receiver. I havn't seen much of it recently.

Also, I am hoping that the way Ace UL stock attaches to the receiver will help mitigate that.

Ultimately, I should probably use an adjustable gas block on the upper I use for this lower, so I can modulate the impact.

ILya


Edited by koshkin - February/09/2018 at 10:41
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rancid Coolaid Quote  Post ReplyReply Direct Link To This Post Posted: February/08/2018 at 11:18
Mine is a GWACS, I honestly use it very little.  It has an integral buttstock and putting it together is a departure from normal AR15 lower assembly.  It is very light and mine has held up well - to admittedly mild use.

If I needed a truck gun or something I just didn't care much about - and would almost never be called upon to use in a life-n-death scenario, it would be a good choice.

I think I got mine when Obama looked poised to outlaw AR15s. Now it isn't worth enough to sell.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Marine24 Quote  Post ReplyReply Direct Link To This Post Posted: February/09/2018 at 09:42
Interesting thread.  I picked up a couple of magnesium lowers which are crazy light, but haven't done much with them.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote koshkin Quote  Post ReplyReply Direct Link To This Post Posted: February/09/2018 at 10:43
Originally posted by Marine24 Marine24 wrote:

Interesting thread.  I picked up a couple of magnesium lowers which are crazy light, but haven't done much with them.

Is that from Mag Tactical? or does anyone else make them?

I kinda like unusual materials and considering how good modern composites are, I figured I should ask around.

In principle, I do not see why I would not be able to 3D-Print a lower with some modern plastics.

ILya
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Post Options Post Options   Thanks (0) Thanks(0)   Quote RifleDude Quote  Post ReplyReply Direct Link To This Post Posted: February/09/2018 at 11:08
Originally posted by koshkin koshkin wrote:

I kinda like unusual materials and considering how good modern composites are, I figured I should ask around.

This upper and lower set from V Seven is what I'm using for my ultralight build. It's less than an ounce heavier than polymer, yet made of 2055 lithium/aluminum alloy, equivalent in strength to 7075. They are really nice! The only disadvantage is they're crazy expensive. But, when you're chasing ounces with exotic materials, that's the unfortunate tradeoff.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote RifleDude Quote  Post ReplyReply Direct Link To This Post Posted: February/09/2018 at 11:18
Originally posted by koshkin koshkin wrote:

Originally posted by Marine24 Marine24 wrote:

Interesting thread.  I picked up a couple of magnesium lowers which are crazy light, but haven't done much with them.

Is that from Mag Tactical? or does anyone else make them?



I believe Mag Tactical went out of business and Fostech picked up and supposedly improved on their magnesium uppers and lowers.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote koshkin Quote  Post ReplyReply Direct Link To This Post Posted: February/09/2018 at 11:39
Originally posted by RifleDude RifleDude wrote:

Originally posted by koshkin koshkin wrote:

Originally posted by Marine24 Marine24 wrote:

Interesting thread.  I picked up a couple of magnesium lowers which are crazy light, but haven't done much with them.

Is that from Mag Tactical? or does anyone else make them?



I believe Mag Tactical went out of business and Fostech picked up and supposedly improved on their magnesium uppers and lowers.



Yeah, I saw that.  My current interest is with composites, so perhaps I'll shoot with my JMT lower for a bit and see how it holds up.  I had looked at Polymer80 lower a while back and thought it was too flexy, but this one seems sturdier.

ILya
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SVT_Tactical Quote  Post ReplyReply Direct Link To This Post Posted: February/09/2018 at 12:08
I had a polymer a while back the original calvary 15...... entire lower was polymer and made together..... buttstock and all.  It flexed something fierce and an upper that normally held 1MOA opened up to several MOA with it.   it was a very early attempt and may have been the first polymer in the game.  Sure its changed allot now.  I would image its the lightest available but for something I'd want tight groups on I don't think I'd try it.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote koshkin Quote  Post ReplyReply Direct Link To This Post Posted: February/09/2018 at 13:11
Originally posted by SVT_Tactical SVT_Tactical wrote:

I had a polymer a while back the original calvary 15...... entire lower was polymer and made together..... buttstock and all.  It flexed something fierce and an upper that normally held 1MOA opened up to several MOA with it.   it was a very early attempt and may have been the first polymer in the game.  Sure its changed allot now.  I would image its the lightest available but for something I'd want tight groups on I don't think I'd try it.

I just an upper with a fairly accurate barrel on there.  I know how it shoots with a regular lower, so I will shortly know how it does with a plastic lower.

ILYa
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SVT_Tactical Quote  Post ReplyReply Direct Link To This Post Posted: February/09/2018 at 14:49
Again I think mine was as the dawn of them coming out.... i'm sure they are improved now.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Chris Farris Quote  Post ReplyReply Direct Link To This Post Posted: November/02/2018 at 15:52
We built a pretty light skeletonized AR for our new SS UltraLight.  Not sure how it will hold up in the real world.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote urbaneruralite Quote  Post ReplyReply Direct Link To This Post Posted: November/02/2018 at 17:28
Speaking of durability of polymer, I was always impressed by the construction of toddler toys. Little boys are one of the most destructive forces in the universe. This one was not able to break the polymer lower Grendel I built for his mom. 
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote koshkin Quote  Post ReplyReply Direct Link To This Post Posted: November/03/2018 at 15:44
My JMT polymer lower was holding up pretty nicely until California changed its laws again and I had to take it out of state to stay legal.

In principle, polymer parts can be extremely strong if the right material and right geometry are chosen and they can last for a very long time if they are temperature and UV resistant. 

The real problem for too many plastics is stiffness.  Carbon fiber, conversely, is very stiff, but quite brittle, so its applications are limited for different reasons.  

I ran into an interesting small company at AUSA that is doing very interesting lightweight and stiff structures out of a large variety of materials simply by implementing very advanced geometries.

ILya
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