hey everyone I know this might be a loaded question because of so many opinions and beliefs bUT I am looking to build my first AR ever and I would like it to be one for longer distances
while 300yrds might not seem very far to most of you I only have experience shooting 100 yards nothing further than 150yrds hunting

My ar15 (Springfield saint A2 front sight) CBQ 50yrds and in with a strike force 1-8x

since I have no experience building rifles what so ever I would this process to be as painless as possible

ambi lower (radian, BAD)
two stage trigger cmc
magpul grip
buffer/ stock? WIP

upon further research I am wanting a completed upper with an 18in-20in fluted barrel in .223 Wylde cambering
range 300+ yrds
1 moa or better

I found an Aero Precision https://www.primaryarms.com/aero-precision-m4e1-enhanced-barreled-upper-223-wylde-fluted-rifle-gen-2-18

Whiteoak Armory uppers win the matches at the distances you are interested in. It’s custom so they will give you a expected date of completion.  Reliable trusted company. Link

Good barrel with matching bolt
Good upper with tight barrel fit
Good trigger
Good ff hand guard

Just to get started. Which ones? That’s like the Ford vs Chevy vs Dodge vs Toyota question. Lots of good choice. Have fun with the research.

Attached File


 I just finished this project as a precision build. Here is a breakdown of what I went with.  I picked my parts based on past experience with my bolt guns and also their reputation.
Since a barrel is the heart of a build I went with a Bartlien blank that was machined and chambered by Compass Lake with their CLE chamber.   I opted for a head spaced bolt and a SLR adjustable gas block.

Trigger is the next most important to me so a trigger tech diamond.  

Upper is a Mega MML combo and the lower is also a Mega. I’ve use their parts in most of my past builds. The stock is a XLR same as my bolt gun chassis.  
Optics are personal choices based on use so I’ll skip that

 

Others have already offered excellent advice on uppers, so I'll address your WIP item.  I use this stock on my "precision" guns:  https://www.midwayusa.com/product/1019117750

For a fairweather shooter like me, it's a great stock.  One big drawback is that it's not adjustable, and over the long term the foam will have to be replaced, but for an AR stock I find it very comfortable.  

Attached File

As others have said, WOA upper will have the accuracy you're looking for.  Another alternative is CLE (Compass Lake Engineering).  I bought a CLE 18" complete upper using a Krieger barrel for about a grand.  Have put about 100 rounds through it so far and was actually at the range with it earlier today.  First 4 five shot groups at 100 were .06", .04", .05" and .07".  Unfortunately I kept going and kind of screwed the pooch with my next couple of groups.  But that's on me not the rifle.  This is shooting ADI 69 gr. match ammo and IMI 77gr. Razorcore.

But this gun is set up solely for accuracy/long distance shooting and when you include upgrades and scope I'm probably into it for $3000.  Its got a Nightforce 2-20X scope, a Triggertech trigger, and a Magpul PRS stock.

Australian Outback 69 grain Sierra MatchKing Ammunition



In their 1984 catalog, Sierra Bullets introduced the .22 caliber (0.224”) 69 grain MatchKing HPBT (hollow point boat tail) bullet (#1380).  The 69 grain MatchKing was “developed as a target bullet for testing by military teams in the new M16A2 rifle”1 and the bullet became a popular choice for shooters using the AR-15 in High Power Rifle Competition.






While the US military had experimented with “heavy” FMJ (full metal jacket) bullets for the 5.56mm cartridge as far back as the mid-1960s,  (the Colt/Federal 5.56mm 68 grain FMJ) the .22 caliber 69 grain MatchKing was the first heavy OTM (open-tip match) bullet that was available to the general public as a reloading component for 223 Remington/5.56mm cartridges.  (Hornady’s 68 grain OTM bullet (#2278) wasn’t introduced until approximately two years later.)





Today, several manufacturers are producing factory loaded 223 Remington ammunition seated with the Sierra 69 grain MatchKing.  Among those, is Australian Outback, a commercial division of Australian Munitions.  

This Australian Outback ammunition is loaded in brass cases.  The primer pockets are neither crimped nor sealed.  There is no sealant at the case-mouth nor any visible case-mouth crimp.  The rounds are charged with a short-cut, extruded powder.  The head-stamp reads:

“223 REM   ADI”








Through some simple testing, I determined that the 69 grain MatchKing has a specific gravity of approximately 10.2.  According to Ballistic Performance of Rifle Bullets by Bryan Litz, the 69 grain MatchKing has an average G1 ballistic coefficient of 0.330 and an average G7 ballistic coefficient of 0.169.  The same source states that the “recommended twist for optimal performance” of the 69 grain MatchKing “is 1:9.5” or faster.”


Accuracy


I conducted an accuracy (technically, precision) evaluation of the Australian Outback 69 grain Sierra MatchKing ammunition following my usual protocol. This accuracy evaluation used statistically significant shot-group sizes and every single shot in a fired group was included in the measurements. There was absolutely no use of any group-reduction techniques (e.g. fliers, target movement, Butterfly Shots).

The shooting set-up will be described in detail below. As many of the significant variables as was practicable were controlled for. Also, a control group was fired from the test-rifle used in the evaluation using match-grade, hand-loaded ammunition; in order to demonstrate the capability of the barrel. Pictures of shot-groups are posted for documentation.

All shooting was conducted from a concrete bench-rest from a distance of 100 yards (confirmed with a laser rangefinder.) The barrel used in the evaluation was free-floated. The free-float handguards of the rifle rested in a Sinclair Windage Benchrest, while the stock of the rifle rested in a Protektor bunny-ear rear bag.  The SMOS billet lower receiver used houses a Geissele Hi-Speed National Match trigger.

Sighting was accomplished via a Leupold Competition Series 45x45mm scope adjusted to be parallax-free at 100 yards. A mirage shield was attached to the objective-bell of the scope. Wind conditions on the shooting range were continuously monitored using a Wind Probe. The set-up was very similar to that pictured below.






The Wind Probe.





The test vehicle for this accuracy evaluation was one of my semi-automatic precision AR-15s with a 24” Krieger barrel. The barrel has a 5.56mm Match chamber with a 1:7.7” twist. Prior to firing the  Australian Outback 69 grain Sierra MatchKing ammunition, I fired a 10-shot control group using match-grade hand-loads topped with the Sierra 55 grain BlitzKing. That group had an extreme spread of 0.67”.








Four 10-shot groups of the Australian Outback 69 grain Sierra MatchKing ammunition were fired in a row with the resulting extreme spreads:

0.95”
0.82”
0.69”
0.97

for a 10-shot group average extreme spread of 0.86”. The four 10-shot groups were over-layed on each other using RSI Shooting Lab to form a 40-shot composite group. The mean radius for the 40-shot composite group was 0.28”.


The smallest 10-shot group . . .









Just for kicks and giggles, I also fired some statistically insignificant 5-shot groups off the bench from a distance of 100 yards.  The cherry-picked group of the bunch had an extreme spread of 0.384”.




.......

IMI “Razor Core” 77 Grain OTM, LR, Mod 1







This load is topped with a 77 grain OTM bullet with a cannelure.  The case mouth is sealed and the primers are crimped and sealed.  When chronographed from the 20” Colt barrel, the load had a muzzle velocity of 2866 FPS with a standard deviation of 21 FPS.

A 10-shot group group fired off the bench from my Lothar-Walther barreled AR-15 at a distance of 100 yards had an extreme spread of 0.95”.








….