How to build a lightweight ar15.

Not exactly lighter, but I suggest skipping the crappy plastic receiver. A modern lightweight alloy receiver will only weigh slightly more, but you will end up with a much more credible build. I personally see a cheap poly lower and think "junk toy gun".

Thompsoncustom said:

So do you also think junk toy gun when you see most of the gun handguns on the market these days?

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Handgun frames aren't subjected to the potential forces that a polymer lower receiver can be subjected to. Until a Glock weighs 4-5 pounds and has a receiver extension and stock hanging off the back that is only supported by the polymer itself, that is a completely invalid comparison.

A properly-engineered polymer lower could be fine, but there's no way one can make a case for any polymer lower based off of the use of polymer in handguns.

So what does New Frontier do with their lowers to ensure they don't break in the common failure points of other polymer lowers?

Thompsoncustom said:

So do you also think junk toy gun when you see most of the gun handguns on the market these days?

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No, thats why I specified "cheap poly lower". We both know I was referring to AR15.

Doubled.

Thompsoncustom said:

Oh i know you where referring to only ar15 polymer lowers but glocks infact are super cheap to make it cost less to make a complete glock than it does to buy the new frontier polymer lower.

Are they that much better than other polymer lowers i dont know but they do have a lifetime warrenty and theres video of them being ran over with a truck and coming out undamaged. I dont think there as strong as a forged aluminum one but i do think there as good as any glock frame.

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Poly lowers generally function fine, but they also commonly break at the buffer tube threads, there are many instances of this exhibited online. If the target goal is lowest weight regardless of durability, then poly makes sense. If the goal is the lightest/quality rifle, poly is a fail. Mag tactical lowers are only 5.8oz, inexpensive too.

Thompsoncustom said:

Mag tactical would have been in consideration for the article if the company didnt go belly up from the lowers breaking.

They did have some really good ideas with there magnesium alloys tho.

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Ah thats too bad. Battle Arms Development looks good, but kinda pricey for a 3oz weight savings though.

I'm thinking about one of these for a lightweight assembly with a Hera CQR Buttstock which will be featureless here in Kali and distribute the stress to the grip mount too ...

http://www.tnarmsco.com/liberator-80-receiver-blank-w-jig/

A properly-engineered polymer lower could be fine, but there's no way one can make a case for any polymer lower based off of the use of polymer in handguns.

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The Cav Arms style lowers were about the best polymer lower made. The stock, lower, and grip were all molded as one piece. Those would probably be a pretty solid choice for a lightweight build that would not suffer from the structural problems seen with most polymer lowers.

GWACS still makes them.

http://gwacsarmory.com/

Both Taliv and I have lightweight build threads. I managed 4.32lb (although the magnesium upper I used is no longer made): https://www.thehighroad.org/index.p...ultralight-ar-build-pics.766900/#post-9701047

People who pick it up think it is a toy.

I've been using mine for 3 years now with no issues. I'm debating shaving almost an ounce more off with a titanium barrel but.

Mike

Did you actually build the rifle in the article or just add numbers?

Justin said:

The Cav Arms style lowers were about the best polymer lower made. The stock, lower, and grip were all molded as one piece. Those would probably be a pretty solid choice for a lightweight build that would not suffer from the structural problems seen with most polymer lowers.

GWACS still makes them.

http://gwacsarmory.com/

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The cav15 also saves a significant amount of weight not only through being plastic but also through all the parts the monolithic lower elimates. Used in conjunction with a lightweight bbl and a low mass BCG you can build an extremely light "normal" looking rifle.

My lightest AR-15 weighs 5lbs 14 ounces. I didn't built this rifle with the intention of making the lightest possible gun, but it is a fairly light rifle. It has a relatively heavy barrel, and the weight I quoted was with an Aimpoint mounted to the rifle. The key to keeping this rifle under 6 pounds was the fact that I built an SBR! Chopping off half of the barrel length for this .300 BLK certainly shaved a few pounds off the rifle!

Every so often I toy with the idea of doing a lightweight build, but always come away disappointed that the cost usually results in a rifle where the biggest weight reduction is in my wallet. So last night I got bored and specced out a lightweight build using the Cav Arms lower.

Here's what I came up with:

Lightweight Parts List Cost
GWACS CAV Arms Mk II Lower $129.00
PSA Slick Side Upper Receiver $59.99
PALMETTO STATE ARMORY LPK-G - 7200 $224.00
PSA 16" MID-LENGTH LIGHTWEIGHT CHF STAINLESS STEEL 5.56 NATO 1/7 BARREL - 1897 $272.99
PSA AR15 UPPER BUILD KIT - 28084 $39.99
Odin Works 15.5" KMod FDE Forend - - F-15-KM-FDE $230.00
PALMETTO STATE ARMORY 5.56 PREMIUM FULL AUTO BOLT CARRIER GROUP - 8779 $89.99
Milspec Charging Handle $24
PSA LOW PROFILE GAS BLOCK .750 DIAMETER - 516444617 20
PSA AR15 GAS TUBE - MID-LENGTH $12.99
PSA AR15 CARBINE BUFFER - 1177 $9.99
PSA AR15 MIL-SPEC CARBINE BUFFER SPRING - 410 $3.95
Raw Cost: $1,116.89

Not too terrible for a light weight gun with a Geisselle trigger in it, though a bit of Googling tells me that the Cav Arms lowers don't play well with all target triggers, so that could be an issue.

I can build a six pound rifle that is as light as i need to have one. With all of the talk about plastic lowers---I bought a ATI Omni package with a steel reinforced plastic lower. The upper is a standard forged aluminum unit
And has i believe a DC Machine barrel, the intent nwas to shoot it until the plastic lower broke and then replace it with a new lower of aluminum. Fifteen hundred rounds were put throough it in mag dumps, rapid fire on sreel etc. but at that point the rifle was still shooting connecting shots at 50 yards. Not a lot of shooting but enough to convince me this was a neat rifle and it proudly sits in the rack with it's more expensive brothers. The lower has displayed no sign of fatigue or wear.
In my light weight builds faxon LW Gunner barrels are my choice.

I agree that the Cav arms lowers (now GWACS) are one of the best out there regarding polymer. I've heard bad things about some, especially Frontier.

My first AR was made from the factory by Sabre Defence with one of these Cav lowers. It's been good.

Couple years later I bought the GWACS version for $70 and it's been fine too. I don't beat the crap out of them but I don't think I baby them either. The Sabre has a lot of rounds through it without issue. It's a love/hate thing on poly I think.

@SlowFuse: the Cav/GWACS lowers are Nylon 6 like Glocks and are very think where they need to be. Normal dimention lowers in polymer or magnesium have a weak spot at the buffer tube attachment point. Time will tell how the new lithium-aluminum alloy ones work out.

@R.W.Dale, ditch the 10 rd Magpul. It is really heavy. A nice aluminum 10 rounder like a D&H is much lighter.

Mike

The Tennessee Arms poly lower has a brass insert molded into the lower where the buffer tube screws in. It's an 80%, so I can leave as much material as possible in the FCG well. If I use a drop-in trigger, I can make the well just wide enough to allow that to slip in

And, like I said, the stock attaches at both the buffer tube and the pistol grip base, and connects all the rear surfaces. Should be plenty strong enough for a 22WMR upper