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Build a Light Weight 308 AR


imschur

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Jusr weighed the A2 flash hider (FH) w/o the washer...1.8 oz, so just .5 oz lighter  :'(  was hoping for a full 1 oz lighter as reported (maybe of a 5.56?), but oh well.  I wonder if the dpms factory FH offers more accuracy?  I guess I will go with the A2 FH for now, it's also a bit shorter in length, and has more of a muzzle break look to it (no slots under it).

Still waiting several more weeks to go for the Gen 4 upper receiver from NEMO

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  • 1 month later...

Still Waiting for the lightweight upper.  It seems NEMO and SI Defense are...well, doing something different?

As it stands now, I just purchased an 18 inch barrel weighing 2lbs .4 oz  ;D
So my net weight loss is the following:
XM177 Stock -4.0
Bolt -4.0
Handguard -7.0 5.4 oz
Barrel -7.3
A2 F.H. -.5
LW Upper -3.0 (based upon what they have told me, but still a wild card).

My total weight loss would be 24.2 oz.  Please fee free to check my math :)

It's looking like this rifle will weigh about 6.6 lbs without sights or magazine.

Edited by Glockslap
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Thats pretty impressive, if it works out to be accurate, that's between 1.5 and 1.75 lbs lighter than my lightweight 18" build. better not leave it laying on the bench unattended on a windy day or it may blow away. By the way what rail are you using?

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I agree that the weight loss is impressive. <thumbsup> Should we start sending "get well soon soon" cards now, or should we wait till after this rifle beats the crap out of your shoulder? That old CAR stock was nearly punishment on a 5.56, I'm scared of how it'll feel behind the .308 with barely any rifle weight to soak up the kick. I'm surprised you didn't go for the 14.5" barrel w/ pinned BABC for the few extra ounces.

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Thats pretty good, but I think your cheating with that CF FF tube. In it's present state yours is 1-1.25 lb lighter than this one. Funny thing, after building this, I put together my 14.5" .308 carbine, and that one, which weighs 10 lbs, handles better IMO than this. I think the short barrel helps, but I've got a heavier stock on it and it seems to balance better off hand, when shooting on the move. This one with the longer barrel and lighter stock feels a little front heavy to me, maybe once I add a long range optic it will balance better. Of course, I'm not carrying any of these for long distance so my observations are probably different than someone that has to carry one of these for a living.

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I will be adding a more substantial stock, or find another commercial type stock and modify it.  That little nub is uncomfortable even on 5.56's as mentioned.  7 ounces is guaranteed off of the barrel, whether I keep it at 16 or the 18 that is on its weigh.  the SI upper should net some more weight off too.

My dream is begining to come true ;D  I just picked up a set of Magpul plastic pop up sights, and will be weighing them later.

Again, this will be a carryin gun, but I am sure once she is broken in, it will suffice as a "balloon up" situation as well.  It should also be pretty well balanced, since the weight has been removed equally, if you look at the numbers.  As it stands now, it feels GREAT  ;D

Not sure about the "cheating" with the CF tube means? 

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I was just making a poor attempt at humor. What I was implying was that you were going over into competition/ game gun territory. Please don't pay any attention. I'm as impressed as many others, that you've been able to lighten a large frame AR to sub 7lbs stripped. As you say, if you build the basic gun to this weight, and add weight with optics and other accessories, it will not present much of  a problem to take them right off when desired, while on the other hand,  if your stripped gun weighs a lot due to barrel/rail/stock, thats not going to be a practical option. I've never hunted with an AR, and have not found myself walking long distances with them so I'm not really able to appreciate what the 2 or 3 lbs will mean to you after a day of walking with it slung over your shoulder while carrying a pack.

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The FSB is lower than the rear upper rail.  I may need a rise, or taller FSB.

Further, I saved potentially another ounce with a Magpul grip.  I will have the model later.  My 2lb 18 inch barrel arrives today, and I have been told the SID uppers should be available next week.  I'm hoping for at least another 10 ozs off this rig  :o

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6lbs 11 oz even with the new 18 inch barrel with hider on it.  It weighed 1lb 15.4 oz (and ounce lighter than advertised).  So all I need now is the LW receiver + a few other things, but as it stands now it is 6lbs 3.4 oz with sights.  Pics tomorrow  <thumbsup>

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Well that is a good question, since most folks don't care about muzzle flash on a traditional hunting firearm, and 18 inch/.308 has almost fully cooked all of it's powder.

For me, I wanted to keep somewhat with the tradition of the rifle, it *may* reduce some muzzle climb, and the fact that I may consider using it with night vision-as well as the unlikely event I ever had to go defensive with it.

But I could definitely save another 2 oz there, and another 1-2 oz by chopping the 18 down to 16.  All in all, my only penalty (hopefully, slight) will be going to a mid-length gas system (I've already ordered another carbon fiber tube, which will need to be cut down from rifle length to mid).  Hopefully, the slight weight penalty will also help mitigate recoil and pressure to compliment the adjustable gas system.

I think I need to do something about that stock though, and I don't want to add more weight to it, since "irons" will add weight. I have some ideas, but we'll see...

Wouldn't it be a hoot ?- It weighs like a 5.56, kicks like a 6.8, hits like a .308?  8)  I've already had several people say what I am doing is not possible (not here), which I find, well you know-pretty possible  <laughs>

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Your going to have to post your (subjective) opinion of how it feels relative to a standard, 8-9lb .308 AR, once you've had some range time with it. By the way, you probably already know this, but the rail on the DPMS uppers are different heights than what is found on the majority of other uppers, so you may find that the riser is not needed once you switch your upper. 

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It would be nice if those plastic sights would bolt on clean  <thumbsup> and no I didn't know that, so that would be a big plus. 

It's looking like a 6lb 8 oz gun w/o sights and mag, and IDK if I can scare a few ounces off w/o chopping things further.  I thought about cutting/cheesgrating the magwell box, or drilling holes in the charging handle.  I feel like I want 6.5 lbs with the sights, but again, the key will be the upper receiver weight.

We shall see.

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  • 2 weeks later...

Well still waiting on the lightweight upper, so I won't know till I way it.  But the full length carbon fiber handguard I ordered came in, weighing 2.6 ozs heavier than the carbine length. 

Once cut down, I'm hoping for only a 1-1.5 ounce weight penalty to cover the gas tube safely.  Remember, my LW barrel is a midlength, so neither here, nor there  <dontknow> lol.

Any hints on cutting carbon fiber  :o

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