My lightweight 300 blackout build requires some input

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R.W.Dale

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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
 
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.
 
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.
 
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.
 
Casefull said:
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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Weigh a lower, castle nut, retainer plate, pistol grip, buffer tube and buttstock with that lower
 
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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.
 
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Casefull said:
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.
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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.
 
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!
 
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 oz ImageUploadedByTapatalk1454630930.771757.jpg
 
R.W.Dale said:
5DFF8C5C-E7F1-42FC-B282-1F555DA6CEB0_zpsnbvc6hnl.jpg

The upper is now assembled eagerly awaiting the lightweight taccom buffer and the yet to be determined spring.
Click to expand...
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.
 
I have a few of the cav lowers tried to beat one up with a 458 socom upper, nothing gave up.
 
ImageUploadedByTapatalk1455500149.409111.jpg

The rifle is together and ready to begin testing. Thanks to the Tubb CS flatwire spring the bolt closing is very energetic alleviating one of my main concerns that there wouldn't be enough mass to strip rounds from the magazine.

I cannot give a weight number yet beyond its too light for my cheap fish scale to weigh. I will find another and update later but suffice to say the gun is VERY light
 
Well, I'll be.

I'm waiting to hear how this thing shoots and handles stress.

Personally, if I wanted a lightweight AR (and I'm thinking of building one), I'd probably go with a magnesium lower and a Mission First Tactical buttstock. I figure mine would weigh in just under six pounds.
 
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