4 Lb AR-15

[Ted S.]

Anyone have a lightweight build close to this yet? I've been slowly attempting to build a sub 4 lb AR-15 (once complete will be an SBR, but I'm kind of digging the idea of keeping it a pistol (should be about 3.7 lbs or so) for a while).

 

Haven't seen a good lightweight build thread lately, so if you have one, post a pic and weight! I want to see what you've come up with.

[MacGyver]

Gordon did a ridiculously light one a couple of years ago.

[Ted S.]

Yup, Gordon is doing most of the legwork. It'll be running a 1.33 oz buffer, so as long as it cycles fine, that will stay. Can't wait till this thing gets done.

[Clod Stomper]

Out of curiosity, what's the twist rate of that barrel?

[Ted S.]

Out of curiosity, what's the twist rate of that barrel?

 

1:8

[TNWNGR]

what are you planning to use for a receiver plastic or alloy? The first is lighter the second can be lightened if yo have a knowledgable machinest with the correctly sized milling machine. I know a man who wanted to make a flattop receiver but already had a standard carry handle upper and an adventurous mind. Yep he milled the carry handle off then drilled and attached a weaver base with a lightweight kind of steampunk look to it. Shoots good to.

[Dolomite_supafly]

what are you planning to use for a receiver plastic or alloy? The first is lighter the second can be lightened if yo have a knowledgable machinest with the correctly sized milling machine. I know a man who wanted to make a flattop receiver but already had a standard carry handle upper and an adventurous mind. Yep he milled the carry handle off then drilled and attached a weaver base with a lightweight kind of steampunk look to it. Shoots good to.

When I was building mine I was going to have a channel milled down the middle of the rail on top of the receiver as well as any other rails.

 

The first "railed" AR was done exactly like that 30+ years ago by JD Jones. BTW, he is the one who made the 300 Whisper, now 300 Blackout, popular. JD could have been a success too if he didn't insist on royalty fees and refused to have the cartridge certified by SAAMI.

[MacGyver]

When I was building mine I was going to have a channel milled down the middle of the rail on top of the receiver as well as any other rails.

 

The first "railed" AR was done exactly like that 30+ years ago by JD Jones. BTW, he is the one who made the 300 Whisper, now 300 Blackout, popular. JD could have been a success too if he didn't insist on royalty fees and refused to have the cartridge certified by SAAMI.

Seem like a super lightweight build could go even further.  Decide where you're going to mount your optic or whatever and remove the rest of the rail at large by milling it flush.  It's not going to save ounces - though it might shave an ounce or so.  These things are hunts for grams, so every little bit counts.

[Trekbike]

Ted and I are working on his build together. I just thinned out a barrel for him.

 

Since I try to learn something new each day, please comment on the purpose of the machined "rings" rather than a straight metal removal.

[TNWNGR]

Re: the milling rings question. Heat dispersal, rigidity and weight reduction are the foremost reasonings but in some instances it's used in barrel harmonics. As to why Dolomite's done so in the indicated pictures is for him to explain but it's certainly a good looking piece of workmanship.

[hipower]

Re: the milling rings question. Heat dispersal, rigidity and weight reduction are the foremost reasonings but in some instances it's used in barrel harmonics. As to why Dolomite's done so in the indicated pictures is for him to explain but it's certainly a good looking piece of workmanship.

 

I was just looking at the pic and wondering the same thing. Even thought as you did on heat dispersal, but wasn't sure on it.

 

Still is a great looking barrel though.

[Dolomite_supafly]

Because this is a THIN 30 caliber barrel I was hoping the cooling find would reduce the heat in the rest of the barrel. Who knows.

[TNWNGR]

Because this is a THIN 30 caliber barrel I was hoping the cooling find would reduce the heat in the rest of the barrel. Who knows.

Yeah, but my concern with a thin barrel is "barrel-whip", while also factoring in said effects vs. barrel length. I'm sure there's some mathmatical formula to find that information with twist rate and recommended load. In the end though it frequently comes down to trial and error coupled with a dose of best practices of first hand experience.

[Dolomite_supafly]

The barrel OD, at its thinnest, is the same as most AK barrels. So I do not see a problem at least not without a lot of rounds being fired and we have discussed that. The 7.62x39 will likely have more pressures than most 300 Blackouts.

[Garufa]

Barrel weight before and after?

[Ted S.]

Before 23.2 oz, after 18.5 oz.

Edited July 27, 2015 by Ted S.

[TNWNGR]

Before 23.2 oz, after 18.5 oz.

You can open up the inside of whatever flash guard you place on the barrel for a weight savings and a chases a few grams off the receiver as well. What you should be thinking about is a skeletonized hand guard, no sling swivels and the lightest sight set up you can run. Do that and it's really going to be light and snappy.

[Ted S.]

You can open up the inside of whatever flash guard you place on the barrel for a weight savings and a chases a few grams off the receiver as well. What you should be thinking about is a skeletonized hand guard, no sling swivels and the lightest sight set up you can run. Do that and it's really going to be light and snappy.

Gordon already made a Ti muzzle device that weighs less than half an ounce. Insanity. The lower is poly, and I'm planning on a 5oz rail. :)

Sent from my SAMSUNG-SGH-I547 using Tapatalk Edited July 27, 2015 by Ted S.

[TNWNGR]

I wondered if you'd decided to go with the poly receiver since this whole thread's about weight saving and that'll save some weight. You can also trim a tad bit off of the poly receiver. If you go with fold down front and rear BUS I recommend the MAGPUL set, I've been very pleased with the set on my S&W 15/22 MOE.

[Dolomite_supafly]

I had a New Frontier Armory that I bought new with the stock and FCG in place. It was my original lightweight build but it cracked at the buffer tube. I sent it back and got one of their billet lowers instead.

 

The Mag Tactical magnesium lowers are coming down in price. It is a great compromise between aluminum and poly, not as light as poly but not as strong as aluminum. I have seen their stripped lowers for ~$125 out the door locally and their stripped uppers for $99.

 

For an upper I would find an upper without the forward assist and you could probably mill off the shell deflector as well.

[Ted S.]

I wondered if you'd decided to go with the poly receiver since this whole thread's about weight saving and that'll save some weight. You can also trim a tad bit off of the poly receiver. If you go with fold down front and rear BUS I recommend the MAGPUL set, I've been very pleased with the set on my S&W 15/22 MOE.

 

I have a set of Magpul's flippy sights on my other AR, they are awesome.

 

For an upper I would find an upper without the forward assist and you could probably mill off the shell deflector as well.

 

Using a 2A Balios lite upper. Mag Tac's upper were too hard to get a hold of when I got the upper.

[Clod Stomper]

I had a New Frontier Armory that I bought new with the stock and FCG in place. It was my original lightweight build but it cracked at the buffer tube. I sent it back and got one of their billet lowers instead.

The Mag Tactical magnesium lowers are coming down in price. It is a great compromise between aluminum and poly, not as light as poly but not as strong as aluminum. I have seen their stripped lowers for ~$125 out the door locally and their stripped uppers for $99.

For an upper I would find an upper without the forward assist and you could probably mill off the shell deflector as well.

I am thinking of one of these for a lightweight rifle.

http://aimsurplus.com/product.aspx?item=XANA3LWT&name=Anderson+Manufacturing+Lightweight+Sport+AR+Upper&groupid=1996

Still has the shell deflector. But it can be milled off. And the price is right.

[Ted S.]

I am thinking of one of these for a lightweight rifle.

http://aimsurplus.com/product.aspx?item=XANA3LWT&name=Anderson+Manufacturing+Lightweight+Sport+AR+Upper&groupid=1996

Still has the shell deflector. But it can be milled off. And the price is right.

 

Should be lighter for sure, and that price can't be beat. If you can find a stripped mag tactical upper, you could save even more weight, but at a cost.

[NoBanStan]

Ignorance talking here, but thinning that barrel won't cause it to wear faster or deform due to heat and pressure?

[gjohnsoniv]

At what point would swiss cheesing a lower become an issue? Upper as well, I'm curious.