My lightweight AR build (second thread)

[Dolomite_supafly]

I am starting a new thread after the last one got derailed a bit.

Anyways I went through and weighed a few parts to give you an idea of weights and dimensions.

The barrel is a 20" barrel that is .56" ahead of the gas block and .64" under the handguards. It maintains that profile to the front of the chamber. The barrel weighs (with the railed gas block, flash hider and gas tube) exactly 2 pounds. I am using a standard A2 flash hider but I might actually just make a thread protector to take weight off, haven't decided. I countersunk the flash hider so it will tighten directly against the barrel shoulder without a crush washer, saving a little there.

The upper receiver (with charging handle and FA) only weighs 8 ounces. I am also debating on milling down the center of the top rail to save some weight there. I will not be using a ejection port cover, not really for weight savings but just that I don't need it.

And while I had the lower apart I squared up the barrel mating surface to hpoefully help with accuracy.

For the bolt and BCG I am going to use a standard bolt. I had thought of using a lightweight JP bolt or lightening a standard bolt but if I do I loose the use of the forward assist. The standard bolt weighs 10 ounces.

I found an old bare bones collapsible stock. The one without any reinforcement ribs. It weighs just 3 ounces and will be good enough.

The standard standard lower receiver weighs 1 pound 9 ounces complete with a commercail buffer tube but no stock. But to save even more weight I think I am going to order a polymer lower. The polymer lower is 7.2 ounces lighter than a standard lower so that is a significant weight savings. If I don't like it I can always use it for my dedicated rimfire.

10 rounds of 55 grain loaded into a stubby magazine weighs 5 ounces. I might be able to shave some weight with a Magpul magazine. If anyone has a 10 round aluminum mag and a short Magpul magazine could you weigh them to see which is lighter.

I am still working on a free float tube. I can save 3 ounces but at the cost of about $130 more. I am still debating on that but I think I will be going all out for this build.

That pretty much covers it other than optics. I would like to find a lightweight magnified scope that is 4x. If not then I will be Using a Burris Fast Fire which weighs 1 ounce. Or maybe a set of Magpul polymer sights.

My goal is to have a gun capable of firing 10 aimed shots while still under 6 pounds. I also set a goal of doing it with off the shelf parts so anyone who wants to duplicate it can. I was going to do some "creative" weigh saving measures but I want anyone to be able to duplicate what I am doing.

Right now I am at 5 pounds 4 ounces with everything but the handguard but with a standard lower. If I go with the polymer lower that drops the total weight to 4 pounds 13 ounces before the handguard. And the handguard I plan on using is only 9 ounces so I should have a complete gun capable of firing aim shots that weighs 5 pounds 6 ounces.

I will post pictures in a few days as the build progresses.

Dolomite

[Dolomite_supafly]

Also, the person in Knoxville with the gas blocks please PM me your contact info.

Thanks

Dolomite

[Magiccarpetrides]

sounds pretty cool man...when i built my "fancy" ar i originally had the same intent...but it got horribly derailed...now my lightweight "ar" is my keltec pistol lol. Keep us updated!

[Dolomite_supafly]

This all started with the barrel that a gunsmith had messed up when installing the front sight. The tried to do it without a jig and the sight was canted very badly. Something else is the chamber is a 223 chamber or 5.56 match as I like to call it. It is a 12 twist barrel which is also something I have been wanting for a while so I can shoot lightweight bullets. And with that twist FMJ 55 grain bullets will be accurate yet tumble upon impact with anything.

Funny how nearly every AR build of mine started with a single, extra part. And in most cases most of those parts were cheap.

When I get it built we need to get together it has been long over due as you are local to me. Or if you want we can grab lunch sometime.

Dolomite

[East_TN_Patriot]

I started a lightweight build using a Plum Crazy lower. It was insanely lightweight. I ended up just slapping a regular upper on it (that was part of my DS Arms saga that assures I will NEVER spend a dime with those idiotic crooks again) and it was around 7.5 pounds unloaded IIRC. I had a buddy who wanted it more than I did, so I sold it to him and built a different rifle. I think PCF changed their name to New Frontier Armory - I guess they figured out their original name was pretty lousy. If I ever run across one of these lowers again and the price is right, I'll likely pick one up and do another lightweight build. I'm looking forward to seeing the pics of your build when it's done.

[Dolomite_supafly]

Joe Bob Outfitters has them for under $55 shipped.

Dolomite

[RichardR]

I have a couple of sbrs that weigh in right at the 5lb mark and a m4 that sits right at 6.5lbs, all of them are forged uppers and lowers though so I could probably get the weight down on them if I wanted.

However after the Bushmaster carbon fiber fiasco I have been a little leary about trying any of the poly/fiber uppers or lowers.

[TN Outlaw]

sounds awesome looking forward to some pics

[kwe45919]

......also posted this in the Frontier thread......

.......why haven't you consider the Frontier poly lower? Especially since you had seen mine and tweaked the trigger.......The lower is sitting in the closet if you want to "borrow" it for the weight comparison thing, especially since it's a complete lower. It's not doing anthing but waiting on me to get off my butt and get it another Upper, that ain't happenin' anytime to soon. If you want it, holler at me.

[Dolomite_supafly]

......also posted this in the Frontier thread......

.......why haven't you consider the Frontier poly lower? Especially since you had seen mine and tweaked the trigger.......The lower is sitting in the closet if you want to "borrow" it for the weight comparison thing, especially since it's a complete lower. It's not doing anthing but waiting on me to get off my butt and get it another Upper, that ain't happenin' anytime to soon. If you want it, holler at me.

When I get the upper done I will meet you somewhere. All I want to do is attach the lower to the upper then put it on a scale. At some point I start to reach a point of diminishing returns. Like is 3 ounces worth $100 more in cost for the lighter free float tube. I am torn between MI, Troy and Samson.

I know the polymer lowers are 7 ounces lighter than a standard aluminum lower but I already have an aluminum lower ready to go. So I could take the $125 it would take to build the polymer and put it towards the fore end I really WANT.

The difference in weight for the whole gun between polymer and aluminum is 5 pounds 13 ounces versus 5 pounds 6 ounces. And that includes the FF tube I want. Either way the gun is going to be light and something anyone can do.

Dolomite

[kwe45919]

NP, just holler at me when you want/need it.

[Dolomite_supafly]

Right now I am on the hunt for a lightweight free float tube/rail.

I am heading to Predator to check some of theirs out.

Dolomite

[mikegideon]

I assume the one with the $130 price tag is carbon fiber?

[Clod Stomper]

Also, the person in Knoxville with the gas blocks please PM me your contact info.

Thanks

Dolomite

PM sent.

[Dolomite_supafly]

So I have got everything assembled and test fired now. It is not Wolf friendly and will not cycle enough to even lock on an empty magazine. That is fine by me because I plan on reloading anyways. It does cycle 62 grain M855 great.

I have decided to go cheap rather than light, I knew I would have to pick one. But as it stands right now it is 6 pounds on the dot without optics and 6 pounds 4 ounces with the Fast Fire. I used a $35 Model 1 Sales free float tube that weighs a metric ton compared to some of the purpose built lightweight rails.

I am thinking I can shave a few ounces by going with a minimalistic gas block rather than the chunky aluminum one I currently have. And bring it in under 6 pounds with the Fast Fire.

Here is a picture at 6 pounds 4 ounces:

If I decide I am actually going to use this I will spend the $180 for a lightweight rail and another $150 for a complete polymer lower.

As it stands right now I have less than I expected I would have in the entire upper not including the BCG. Now I need to work up some handloads and take it to the range to see how it performs. I know with the extra barrel I can push the 53 grain SMK's to probably 3400+ fps or 40 gran Vmaxes to 3600+ fps.

Dolomite

[Dolomite_supafly]

Just another update.

I added a carbon fiber free float tube today (thanks Jeffsig). The new weight is 5 pounds 7 ounces or 5 pounds 11 ounces with a red dot.

Dolomite

[kwe45919]

Nice...comming along fast. Get pics up of the CF tube...

[Guest ADAM]

Don't thank jeff thank me since that carbon fiber came off my gun lol. What are you going to do with the tube that was on your rifle. I like that plain jane looking one.

[mikegideon]

Those Model One tubes may be heavy, but they're real good for the money. I have one of their rifle length tubes on my heavy rifle.

Carbon fiber beats a light rail system in weight, correct?