AR Build, Please comment

[WoodlandShooter]

So, I have a "spare" RRA A4 carbine in the safe. I have been thinking of tweaking it a little. my idea is a bit of a hodge podge between a Varmit, Mk-12 SPR, three-gunner...more of a short, solid, mid range support rifle than anything

 

The build would be based around a 77 Grain OTM bullet at ~ 2650-2700 FPS. Max range is about 700 yards.

 

As I am not too worried about weight, I am considering a 16" 1/8 twist Bull Barrel...just not sure whos to get... I do want it to have a mid length gas system tho.

 

I also want a contiguous top rail so I can run series optics if necessary. SO either thinking a PRI fore-end with rail, or a VLTOR CASV, or a POF M-Rail...looking for recommendations here. I do want a full rifle length front end

 

Stock could be anything...but I do like the Mag Pul PRS I have on the 243WSSM...it is a little heavy, but it would ballance out the Bull Barrel.

 

Primary optic would be a 30mm "something" Preferrably  variable 2.5-10 x 32...nothing too crazy...bit I do want it in Mills, and possibly have a reticle to at least -9 mills of drop it does not need to have adjustable turrets.

 

Back up irons are already set...will have Knights Armament 45 degree offset flip ups.

[Jim the Plumber]

Might consider a 18" SS 8 twist on the mid gas. I like a little more length  and a little less weight, so an 18" barrel in a mid weight profile is a better balance.
Take a look at Seekins rails/ hand guards. Great product and enough options to fit most tastes/ needs: http://www.seekinsprecision.com/
Nightforce has your scope: http://nightforceoptics.com/compacts/2-5-10x32-nxs-compact-riflescope/

[Heredoggydoggy]

I'm a big fan of PRI stuff.  When I built my 6mmx6.8 SPC AR, I used a lot of their stuff.  In fact, back when I got my 6.8 SPC, the word was that the only mags that functioned reliably in the 6.8's were PRI mags, so that's what I got.  Good company, fast shipping, etc.   

[WoodlandShooter]

Might drop the Bull Barrel Requirement.

Now looking at a Lilja Recce Barrel and a Krieger Recce barrel..subtile differences...

Lilja: 1/8 twist, and carbine length gas $475

Kreiger: 1/7.7 twist, mid length gas $575

[JLR]

Might consider a 18" SS 8 twist on the mid gas. I like a little more length  and a little less weight, so an 18" barrel in a mid weight profile is a better balance.
Take a look at Seekins rails/ hand guards. Great product and enough options to fit most tastes/ needs: http://www.seekinsprecision.com/
Nightforce has your scope: http://nightforceoptics.com/compacts/2-5-10x32-nxs-compact-riflescope/

I'll 2nd what JTP has said with the exception that I'd run an 18" with a rifle length gas system.  For a multipurpose rifle, the Seekins SP3R handguard can't be beat.   For a scope, take a look at the Vortex 2.5-10 along with the Nightforce as it's a really nice little scope.

[Biggerhammer]

18" mid weight, rifle length gas, 8 twist. Might want to check out the Rainier Arms Ultra Match SPR barrel.

Noveske NSR or a MI SSK Key Mod.

Plenty of 2.5-10's to choose from.

[Fuzzy]

Im going to echo what JTP and JLR said i think 18" barrel would be my choice. I and i vote Seekins stuff as well, great products and a nice guy as well. As far as scope i would look into SWFA  3-15x42, good glass and has 10 mils down in the reticle. Not a bad price either.

[WoodlandShooter]

I ran some ballistics on a 77 grain SMK, (G1 BC = 0.362) and it only gives about 19 yards of extra supersonic range on a standard day...

Assumptions...

18" barrel would have a MV of 2700, therefore at 688 yards, it hits 1195 FPS
16" barrel would have a MV of 2650, therefore at 669 yards, it hits 1196 FPS

not sure the extra 2" is really worth anything..

What i am hung up on is barrel profile...I would like to wring as much accuracy as I can out of it..so I am torn between a full bull barrel and a turned down (Recce) barrel

[Heredoggydoggy]

A bull barrel is good for shot-after-shot accuracy at a bench, but for one or two accurate shots in a hunting situation, it's not worth lugging that much extra weight.  I've shot my standard weight ARs until I couldn't hold my hand on the hot barrel, and saw no difference in accuracy... 

[WoodlandShooter]

not too worried about weight. My 270 weighs 14 pounds wet....so a 10 pound AR would feel like a feather.

My next question...

Is it even possible to get an AR to shoot under 0.5 MOA??? My 243 WSSM is close, but it is an off the shelf upper so I think it is possible...

Yes, I want something that is very accurate shot after shot. I also want it to be "usefull".

I dont need a Mk12 clone. I also may use Hornady 75gr BTHP's at 2600. That gets a carbine to just over 700 yards of supersonic range

anyone here have experience with a RRA Bull Barrel??

[Heredoggydoggy]

I hefted a RRA rifle with a Bull Barrel once, and it was a boat anchor.  But then, I'm pretty sensitive to weight.  If you aren't, go for it!  I took my RRA Coyote Rifle out to test it, and all I had was a 1-3 Power CQB optic, and at 100 yards all I could do was superimpose the circle-dot reticle on the 8" bullseye target, and I was getting 1/2" groups.  With a fine crosshair target scope it would have done better! 

[Jim the Plumber]

AR @ 1/2 MOA is doable. Quality barrel, trigger, optics will get you there. Balance, ease of swing, point ability tend to favor the 18" medium weight.

[WoodlandShooter]

or, I may just stick with the barrel (16" heavy) that is on it...spend the money on a decent optic and trigger instead.

[Craig]

5 shots 100 yards. Didn't measure it but its tight. 18" Rainier arms Match barrel. Next one will have a ultra match barrel. It's all about the trigger. Geissele triggers are awesome.

[Heredoggydoggy]

or, I may just stick with the barrel (16" heavy) that is on it...spend the money on a decent optic and trigger instead.

An RRA 2-stage NM trigger or a Timney Trigger will go a long ways to getting your AR more accurate.  You'd be surprised at the difference!