Building AR for long range

300whisper

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Welp since we are sharing photos...here you go OP. Give you and idea of what your build will possibly look like. One on far right.


2A2CB56E-A5BE-4276-AC83-2A21EAE43B25.jpeg
 

300whisper

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Of course our barrel. We choose the stiffest upper we can find. I would run our AR10 against most bolt guns.

Is that the barrel that has the hollow outer core with tubes running down parrellel of the inner barrel? Looking at it from the muzzle end it looks like a honey comb???
 

chanceinmt

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Feb 3, 2016
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western Montana
I run 6.5 Grendel thru a Wilson Combat 18 inch hunter wt barrel with a BCM bolt carrier in an Aero Precision upper/lower that is heat fit to the receiver. A 16 inch SixFive Arms barrel w/ BCM bolt carrier and BCM upper also heat fit, both wear a Magpull CTR stock. I am within 1 MOA at 500 yds with a Leupold VX6 2x12x 30mm scope. I am getting 2540 avg speed with Hornady 123g ELD M bullets in the 18 and 2505 avg in the 16in barrel with ES of 8 to 10. Handloaded with 31.2g CFE 223
 

amyjune

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Mar 22, 2012
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So Cal
I just built an AR10 in .308. It is an Aero lower, Moriarti upper with a 20" Stainless Barrel. I used different companies for the upper and lower due to impatience with the part shortage and wait time. I put a Razor 3-15X42 with a mildot reticle on it. I shot it for the first time last week to get it zero'd at 100 using commercial ammo. I will post later when I have a load and spent some time with it... So Far, it looks promising, I hope to get it out to 800 yards... if this set up is unsatisfactory I will maybe try an Aero upper in 6.5...
 
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tacomHQ

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Apr 3, 2013
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Illi-noid
Is that the barrel that has the hollow outer core with tubes running down parrellel of the inner barrel? Looking at it from the muzzle end it looks like a honey comb???
Overall “yes”:
It’s a solid barrel that is cored. It has another primary advantage on an AR- it runs cooler. In this case actually “ cooler” as it is a radiator not an insulator. Rex does a great video talking about the barrel and the results of shooting the AR with multiple factory rounds is discussed.
 

300whisper

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Overall “yes”:
It’s a solid barrel that is cored. It has another primary advantage on an AR- it runs cooler. In this case actually “ cooler” as it is a radiator not an insulator. Rex does a great video talking about the barrel and the results of shooting the AR with multiple factory rounds is discussed.

I watched that video. Awesome review by Rex, and cool product.
 

bullet man

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Oct 23, 2019
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dallas ga
the short answer for a 308 get a repr by lwrc they compared it to a Ruger precision bolt gun and it was a tie in the accuracy department. The only problem is it costs 4000 dollars.
 

762x51

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Jan 8, 2016
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NC
there's lots of stuff you can do to make them accurate. the rules are pretty much the same as bolt guns, but bolt guns are little more forgiving since there's less moving parts. you need a solid platform with as little movement in everything as possible. it's tough to with AR's because they're piles of aluminum, metal and plastic held together with a bunch of tiny springs and detents and set screws.

i think the most important pieces are the trigger and barrel. i think i'd go 20-24" on the barrel to get as much velocity as possible. buy american parts from quality manufacturers. (BCM, spikes, rock river, daniel, ranier arms, white oak, lots to choose from). i would steer clear of ebay deals lol.

i dont think you can do anything to the upper receiver besides lap the face. wheeler makes a tool that costs around $30-40 i think. i have one and i've lapped a few receivers but i've never tested it to see if it does anything.

you want as little slop in the upper/lower receiver as possible. try to find a matched billet set. you can also have a smith tig weld the take down pin holes in the upper and mill them to fit in the lower with as little clearance as possible. then put them together and re-drill the take down pin holes to match the holes in the lower. never had it done, but i've heard of folks doing it on other forums.

you can also bed or loctite the barrel extension into the upper. again you want as little slop as possible.
 

Cemetery21

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Jan 10, 2021
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Southwest MO
Aero (and maybe others) make a lower receiver with a screw to set the upper/lower tightness.
I've shot bench guns for 35 years that had some minor play between upper and lower and it doesn't seem to affect accuracy with a heavy rifle on bags. There are a few ways to tighten the upper/lower fit if you don't spring for a matched set (or if your matched set comes with a little play).
 

ntsqd

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Upper SoKA
I don't have any understanding for why upper to lower fit needs to be tight. There's likely a good reason that I'm missing (other than user confidence in the firearm), but to my way of thinking the important part is the upper's fit to the barrel and the BCG as all of the important interactions happen there.

None the less, a couple of my builds have featured that little polymer wedge. There a few vendors who offer a drilled & tapped grip screw with a set screw in the center of it. Running the set-screw out when assembled takes any vertical slop out of the upper to lower fit. I *think* that I have one somewhere, but I've not tried it.

I've used a Seekins IRMT-3 monolithic upper/handguard on a couple builds with good results. I used them specifically to get the flat bottom on the handguard. Other builds I've used Aero or a generic thick walled uppers with Apex Gator Grip handguards.
 

bamban

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Austin, TX
I don't have any understanding for why upper to lower fit needs to be tight. There's likely a good reason that I'm missing (other than user confidence in the firearm), but to my way of thinking the important part is the upper's fit to the barrel and the BCG as all of the important interactions happen there.

None the less, a couple of my builds have featured that little polymer wedge. There a few vendors who offer a drilled & tapped grip screw with a set screw in the center of it. Running the set-screw out when assembled takes any vertical slop out of the upper to lower fit. I *think* that I have one somewhere, but I've not tried it.

I've used a Seekins IRMT-3 monolithic upper/handguard on a couple builds with good results. I used them specifically to get the flat bottom on the handguard. Other builds I've used Aero or a generic thick walled uppers with Apex Gator Grip handguards.
Here is my mod to keep the BCG centered. The uppers I use are the heat-to-fit BCM to competition barrel extensions from Whiteoak Armaments. The BE is 0.300 longer, and 20 TPI instead of the Gi 16 TPI. The BE is like a miniature AR308 BE.

20200827_195040.jpg

20200827_195022.jpg


It goes without saying to accommodate the sleeve, the buffer tube must be bored out.
 
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TXTrained

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Jan 22, 2019
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89
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Brazoria TX
We regularly demo 500yd - 600yd hits when using our AR15--- given the ammo the gun likes-- stock POF. Our main focus is the optics being able to go CQB to 500 yds instantly with any "red dot" or any optic. In this case the optic is the unit in front of the scope -- Alpha TARAC. We build those custom to any gun allowing an instant switch to a second point blank range.
It gets interesting when we get to a larger weapon like a 6.5Creed or the .260Rem pictured. We demo a 100yd round than an instant 1000yd round on a man size target. To clarify- we don't demo- the operators are the shooters. A fun note: we were demoing with a sniper team and ran the 100yd impact and jumped to the 1000-- guys in the pit at the 1000-- he shoots three rounds... the pit guy comes back over the radio "you just dropped a 3" group". Made the shooters day, year, still talks about it.
Lucky --- a bit.
Do we consistently engage man size guys at 1000'yds-- every time we go out for demos. We have engaged 1500yd targets regularly- as long as we can see splash. Will the guns shoot sub 3/8moa-- "yes". With factory ammo and more than likely more than one type. Several top manufacturers will produce AR's with these capabilities.
We do press in every extension into the upper. Switch over to a Savage style nut system. Run a "very" adjustable gas block. Of course our barrel. We choose the stiffest upper we can find. I would run our AR10 against most bolt guns.
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