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Old January 29, 2016, 11:37 PM   #1
R.W.Dale
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My lightweight 300 blackout build requires some input

On certain small parts.

First the build so far as it pertains to lightness

Poly Cav15 lower
Whiskeyarms aluminum bolt carrier
Taccom lightweight buffer
Standard LPK
No FA or dust cover upper
Triangle handgaurds

Two things I am in need of. A good but lightweight .750 adjustable gas block. Recommendations welcome

And the wildcard a buffer spring. Should I just stick to mil spec here or go stiffer because of my ultra low mass bolt carrier and buffer
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Old January 30, 2016, 09:40 AM   #2
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Can't recommend a gas block, but I'd say a stiffer spring would be a benefit.

The biggest flaw in Poly lowers is breakage at the buffer tower. Now I'm not familiar with the Cav15 lower, so it may have metal reinforcement at critical points. But such a light weight buffer and BCG is going to bottom out hard on the receiver extension and put a lot of stress on the tower.


Good luck, I'm working on my light weight build myself using an ATI Omni poly lower.
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Old January 30, 2016, 10:35 AM   #3
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This particular lower has an integral fixed buttstock and buffer tube. I have never heard of a failure of one. They are thicker in all the critical areas to the point of requiring special long takedown pins

http://www.gwacsarmory.com/lower-receivers-ar-15/

Obviously the gas will need to be carefully regulated.
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Old January 30, 2016, 11:51 AM   #4
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Oh ok, I'd seen those but didn't register that's what you were using. The guys at InRangeTV have reviewed them and used them in competition. One of which ran fine in a 2 gun match after being shot in a previous test.

So yeah, seems like your gas is going to be the biggest point, and that's beyond my scope of knowledge.
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Old January 30, 2016, 07:55 PM   #5
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How much weight do you save with a poly lower?
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Old January 30, 2016, 10:35 PM   #6
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Originally Posted by Casefull View Post
How much weight do you save with a poly lower?

Between a pound to half a pound depending on the configuration you're comparing to
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Old January 30, 2016, 10:48 PM   #7
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I just weighed a stripped forged lower I have laying around and it weighs 8.7 oz. So how can a poly lower be one half to one pound less. There is obviously little weight savings going with a poly lower. One is giving up a lot for a couple of oz. of wt.
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Old January 30, 2016, 11:18 PM   #8
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My lightweight 300 blackout build requires some input

Quote:
Originally Posted by Casefull View Post
I just weighed a stripped forged lower I have laying around and it weighs 8.7 oz. So how can a poly lower be one half to one pound less. There is obviously little weight savings going with a poly lower. One is giving up a lot for a couple of oz. of wt.

Weigh a lower, castle nut, retainer plate, pistol grip, buffer tube and buttstock with that lower

Last edited by R.W.Dale; January 30, 2016 at 11:24 PM.
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Old January 31, 2016, 06:17 PM   #9
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What do those parts have to do with the weight of the lower? Isn't the only difference in the weight of the poly lower versus the aluminum Lower? Are those parts also poly? I guess I am ignorant of poly lowers.

Last edited by Casefull; January 31, 2016 at 07:20 PM.
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Old January 31, 2016, 06:36 PM   #10
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My lightweight 300 blackout build requires some input

Quote:
Originally Posted by Casefull View Post
What do those parts have to do with the weight of the lower? Isn't the only difference in the weight of the poly lower versus the aluminum Lower. Rather than obfuscate how about the difference between a poly lower and aluminum Lower.
You are making this painful

Because all those other parts are integral to my lower

Which has been covered quite throughly above already.

A polymer traditional lower saves virtually no weight. A cav15 lower on the other hand saves quite a bit, with most of that weight being in the miscellaneous parts I keep mentioning to you above.
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Old January 31, 2016, 07:24 PM   #11
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Thanks for educating me R. W.
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Old January 31, 2016, 07:31 PM   #12
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I sorta wish I hadn't seen this thread because now I find myself wanting one of those poly lowers. I swear, every time I visit the internet it costs me money!
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Old January 31, 2016, 07:39 PM   #13
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Back to the subject at hand. The Tubb flat wire spring. Is it for carbine AND rifle length buffer systems. Details are scarce
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Old January 31, 2016, 07:42 PM   #14
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Originally Posted by Elkins45 View Post
I sorta wish I hadn't seen this thread because now I find myself wanting one of those poly lowers. I swear, every time I visit the internet it costs me money!
It doesn't have to. It could be the one of the lowest cost options out there...

https://www.rainierarms.com/gwacs-ar...lower-receiver
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Old January 31, 2016, 07:44 PM   #15
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The upper is now assembled eagerly awaiting the lightweight taccom buffer and the yet to be determined spring.
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Old January 31, 2016, 07:45 PM   #16
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Originally Posted by strambo View Post
It doesn't have to. It could be the one of the lowest cost options out there...



https://www.rainierarms.com/gwacs-ar...lower-receiver

It's a smoking deal. I ordered mine from here and the low price certainly helped
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Old February 4, 2016, 08:08 PM   #17
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The aluminum bolt carrier and lightweight buffer have arrived.

The carrier is a thing of beauty and quite picture worthy. Fully assembled it weighs a mere 4.2 ozImageUploadedByTapatalk1454630930.771757.jpg
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Old Yesterday, 04:42 PM   #18
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Quote:
Originally Posted by R.W.Dale View Post


The upper is now assembled eagerly awaiting the lightweight taccom buffer and the yet to be determined spring.
I have one of those on the way to my FFL right now. For $89+$8 shipping +$25 transfer fee I figure it would have to be pretty terrible not to be worth it just for fun. Seems to me this has all the advantages of a polymer lower without the main disadvantage of one, namely buffer tower breakage.

I don't think I'm going to invest in that super-engineered low mass carrier. I'm just going to transplant my 16" skinny barreled 223 upper onto it.
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Old Yesterday, 08:31 PM   #19
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Awesome. Keep us posted.


In the meantime I have a Tubb CS flat wire buffer spring en route and a syrac adjustable gas block
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Old Yesterday, 08:40 PM   #20
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I have a few of the cav lowers tried to beat one up with a 458 socom upper, nothing gave up.
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Old Yesterday, 11:19 PM   #21
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I have a few of the cav lowers tried to beat one up with a 458 socom upper, nothing gave up.
Really? That's interesting and hopeful info for my future .450 Bushmaster build.

The more I look at these lowers, the more I want to replace my ATI Omni gen 1.
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