Is 8.0lbs possible for an AR10 with these specs?

[Hygienist]

I'm considering an AR10 build, based off the Mega MATEN .308.  My desired goal weight is right at 8.0lbs, without a mag inserted.  Would it be possible, with the following?

16" Medium contour barrel (2lb 5oz) (Rainier Select 16" 308, to be specific)

13.8" Modular Rail (13oz)

Standard 5.6oz buffer

B5 SOPMOD stock (let's say 0.75lb)

Could this make weight?  Or will it be going over?

[Matt.Cross]

It's hard to say definitively whether you could or couldn't. You could probably attain that weight with extreme weight cutting measures, but you might not get reliable function out of it.

[Jgun]

I'm thinking that your going to be between, 8.5-9LB as described. But I'd certainly like to be proven wrong. I think you should build it just to prove that it can be done.

[Robocop1051]

You can make your rifle lightweight, high quality or inexpensive... Choose two!

[Hygienist]

Thanks for the replies.  Expense is not a concern, but I'd rather not build this at all if it doesn't make weight.

I'm trying to use the online AR weight calc

http://vuurwapenblog.com/calc.html?Lower=17.4&Tube=3.7&Buffer=2.9&Upper=9.2&Barrel=32&GB=1.6&BCG=11.5&CH=1.5&Stock=11.5&Handguards=-2.8&Optic=0&Light=0&RearSight=0&FrontSight=0&MD=2.1&VFG=0&Can=0&Mag=0&Ammo=0&GL=0&Bipod=0&Misc=13&output=6.012499999999999

to try to see how much it weighs.  I built it as I would an AR10 and then added extra weight according to specifications.

Are the receivers and the BCG the only extra sources of weight?

Mega MATEN lower/upper: 11.8oz more than a AR15 upper/lower

AR10 BCG: 7.5oz more than an AR15 BCG

Adding the 19.3 extra oz puts it right at 8.03ish lbs.  Would there be more sources of weight?  I'm guessing there will be. 

[Jgun]

If money is not a limiting factor, there is no doubt you can build a .308 AR under 8 lbs, I just don't think you'll do it with those components, but I could be wrong. If not mistaken, I think there's a member currantly doing a build that is under 7 lbs.  If you aren't locked into those specific compmnents, you could always build it as you've listed, and if you don't make your weight, swap out a few components for lighter ones. By the way, I think that most here would agree that the difference between an 8 lb and 10 lb gun is noticable, but I don't think an 8.5 will feel very different from an 8 lb gun. besides total weight, the balance of the gun will have  a noticable effect on how well the gun hancles for you.

[NoFail]

JP low mass bolt carrier will save you, I think it's 4 maybe 4.5 oz. Their light contour 16" Supermatch is 7.2 lbs, I could be wrong about that, memory sux... They have this new Silent Captured spring that replaces traditional buffer design, I don't have that, don't know the weight but looks like it could be light  <dontknow>

If Cha-Ching no object call and talk to them. So far their LMOS BCG works great in mine, barrel is all about accurate too. I'm using Magpul UBR and it's plenty heavy but it balances out the weapon and is tough as nails. I think it probably weighs in at about 10 lbs. (UBR has to be the big difference) empty before I thru the scope on. JD Machine receivers light and I bet lighter than MATEN, and their 14" hand guard is extremely light weight, the smooth tube one. Not trying to sell u or justify what I did just forwarding what I know. Anyway, so far I'm very happy with the components themselves. Oh yeah another thing is I chose Slash's Heavy Buffer CAR-10 XH 6.5 oz. sooooo....... Yeah ultra light weight wasn't my ultimate

goal, just light enough, which it is to me.

[NYresq]

compared to a 223, everything is larger and therefore heavier. The BCG, the barrel, the buffer tube, the buffer itself, the hand guard and any muzzle device you add will be heavier then the same component in 223 size. I think the trigger group is about the only part that will be the same (depending on brand, some use heavier hammers for 308). Even the grip may require a spacer block to fit some receivers properly.

if you want to keep the weight down, forget the UBR stock. I had one for about an hour before I sold it. It uses a proprietary buffer tube and it weighs a ton compared to something like a CTR stock.

Stay basic and simple and you should be able to get close to 8lbs without optics.

[Hygienist]

Thanks for the input.

So far it seems it's possible :)  My last question is in the barrel assembly.

If I were to tell a barrel guy to make an AR15 barrel and an AR10 barrel both with .750" OD contour, would they weigh the exact same, or would the AR10 weigh more due to heavier barrel extensions or whatever?

I'm trying to get a general idea but it's a bit difficult.  Looking at Rainier Arms Select barrels in 5.56 and .308, the .308 is 6oz heavier, and from the pictures, looks to be the same-ish contour and appears to have no reason to weigh 6oz more.  In addition, Rainier makes a lightweight .308 that looks more anorexic than a supermodel, but weighs 34oz, which is 3oz MORE than the much meatier looking 5.56.

The two Rainier Selects in question

http://www.rainierarms.com/?page=shop/detail&product_id=2267 5.56 (31oz)

http://www.rainierarms.com/?page=shop/detail&product_id=2687 .308 (37oz)

And the skinny ass lightweight .308

http://www.rainierarms.com/?page=shop/detail&product_id=2421

Any reasons for the weight disparities?

Main question:  For a barrel of the same contour (.750" is the contour of interest, and 16" length), how much more will an AR10 barrel be vs an AR15?

[MikedaddyH]

The breach end of the AR-10 has more metal where the barrel extension threads into the barrel ,also the barrel extension weighs more. 6oz sounds about like minimum weight difference.

[Jgun]

the chamber for a .308 is larger, the .308s bore dia is larger also, so hypotheticaly, if you had two barrels that had identical outside contours and dias, the .308 could in fact be the lighter of the two. But it doesen't work that way, as stated above, the chamber end of a .308 barrel is going to have a larger OD even if the muzzle end were the same. Keep in mind that barrel wall thickness has an effect on barrel whip and accuracy, a .308 barrel with the same OD as a .223 barrel is going to have thinner wall thickness.

[weaponizer]

Here's mine, it weights 8lb 15 oz., you should be able to take 15 oz. off of it..

http://308ar.com/forum/ar-10-pictures/here-we-go-again/15/

[Robocop1051]

Weap is right about his rifle. An ACE AFRX stock and a carbon fiber FF tube would cut the weight alone.

[Fröman]

JP Low Mass Bolt Carrier

JP Silent Spring/Buffer

JP/Syrac Low Pro adjustable gas block

Carbine Length Gas System

CTR or MOE Stock (like Weaponizer)

Lightweight Floated Forend(Lancer

Carbon/Apex/Troy)

Titanium Thread Protector(lighter than muzzle devices)

Maybe those choices will knock a some weight out and compensate adequately for the lightweight components and being a little overgassed. I am not any kind of expert on 308ARs(n00b +25) but I am kind of heading that direction with my own build and I am very weight conscious due to a back injury.