Building a precision 5.56 upper

[jLorenzo]

Other than a good barrel what else can I do to maximize accuracy? Planning on a White Oak, just want to shoot lots of Hornady 75gr handloads, maybe plink with 55gr every once in awhile, nothing fancy.
Already have a basic lower with what I want.

 

[PBWalsh]

Barrel, trigger, bolt, free float (stiff) handguard, some may advise a stiffer upper receiver like a Vltor MUR for overall rigidity while loading into a bipod.

Your WOA barrel is a historically good choice. Maybe consider asking them to spec out an upper and/or build one for you as their reputation is excellent.

 

[jLorenzo]

Barrel, trigger, bolt, free float (stiff) handguard, some may advise a stiffer upper receiver like a Vltor MUR for overall rigidity while
loading into a bipod.

Your WOA barrel is a historically good choice. Maybe consider asking them to spec out an upper and/or build one for you as their reputation is excellent.

How can tell which uppers and handguards are "stiffer"? Type of aluminum used? Also what do I need to consider with the bolt? Ive heard of barrel and bolt matched pairs but I was also under the impression spec wise theyre all the same.
My lower has the Larue MBT2 which I am happy with for the money.
Are there advantages to certain kinds of barrel nuts over the standard milspec?

 

[PBWalsh]

Nice trigger, I love my MBT-2S, very underrated trigger.

For the uppers... the Vltor MUR is a slightly thicker receiver, translating to increased stiffness. Seekins and Aero both produce uppers with their own respective handguard attachments, making it a quasi-monolithic upper. BCM now has their Mk2 upper which shifts some weight forward that is supposed to help out accuracy.

Your barrel nut is dependent on the handguard you get. If you look at a Geissele Mk4, the nut is 2.25” long whereas a BCM MCMR is around 1.5”. G Mk4 is a heavier rail and the BCM is a lighter one. For a full tilt precision upper, you may give more consideration to the heavier rail with the more rigid barrel nut (Geissele). I’m using these two brands as reference because I have used both, there are a ton of great options available. Depending on your use, you may favor one over the other.

As far as matching the bolt/barrel? Thats a better question for @padom or @bigjake83 as they have actually built plenty of precision oriented uppers. Again, WOA is a great resource to sponge off of. I mainly was talking about getting a high quality BCG.

Oh, some folks like using an adjustable gas block in these types of builds. SLR is a fan favorite around here. I have no experience with adjustable gas blocks though.

 

[Molon]

The Essentials of a Precision AR-15

Without making this too complicated, you need three basic components for a semi-automatic AR-15 to produce its best mechanical accuracy (technically, precision): a match-grade barrel, a quality free-float handguard and match-grade ammunition, preferably hand-loads tuned for your barrel. (The free-float handguard doesn’t improve the accuracy of the barrel per se, it simply prevents any outside influence from detracting from the accuracy of the barrel.) Anything after that will not immensely improve the mechanical accuracy of the semi-automatic AR-15, but several things can help you, the shooter, shoot to the level of the intrinsic accuracy of your semi-automatic precision AR-15.

While there are certainly gifted individuals among us that can do amazing things with iron sights, most of us will benefit from using a quality, high-power scope to achieve the highest level of accuracy from a precision AR-15. In order to hit the exact same spot on the target every time, you have to be able to see that you are holding on the exact same spot every time. It’s also important for the scope to be mounted at the proper height and at the correct eye-relief for the particular scope. One of the most common errors I see with scopes mounted on AR-15s is the scope not being mounted far enough forward for its eye-relief. Also, in order to maintain that exact hold throughout the trigger pull, it helps not to be fighting a heavy, gritty, stock trigger. There are a variety of aftermarket triggers now on the market for both standard size trigger pins and the larger Colt trigger pins. Personal preference will definitely play a role in trigger selection. Among the two-stage triggers, I’ve found the Geissele triggers to be the smoothest, lightest, most consistent and most reliable. For single-stage triggers, it’s hard to beat the JP Enterprise Fire Control System. Keep in mind that the JP trigger does require fitting.

Following the scope and trigger selection, some shooters will find that items like aftermarket grips and stocks will help them achieve a better “fit” with their AR-15. (Shooters don’t all come in the exact same size and shape, don't ya know!) Once you’ve put your precision rig together, you have to find a match-grade factory load that your barrel “likes” or better yet, develop a match-grade handload for it.

A semi-automatic AR-15 is not going to shoot as accurately as a precision bolt-gun, but today’s precision AR-15s are capable of a level of precision that is truly outstanding for a semi-automatic rifle. The 10-shot group pictured below was fired from one of my Krieger barreled semi-automatic AR-15s from a bench-rest at a distance of 100 yards. The barrel has a 1:7.7” twist. I used Sierra 55 grain BlitzKings that were hand-loaded on a Dillon XL-650 progressive press. The load was developed using the Accuracy Node Detection Technique. The group has an extreme spread of 0.452”.

...

 

[db2000]

Note the recommended hand guard that will attach directly to this receiver from Seekins I linked. A member has this hand guard and is selling it dirt cheap...and includes an Arca tail! But it now and find this receiver if you want an accurate, stiff quasi monolithic upper!

IRMT-3 Upper

<p><strong>iRMT-3 Upper</strong></p> <p>Designed for extreme accuracy and durability under real-world stress, the iRMT-3 upper receiver allows your barrel to be a true free float system. With the handguard attaching directly

seekinsprecision.com

Accessories - *Price Drop* FS Seekins SP3RV3 15” RPR handguard

In great shape $150 shipped

www.snipershide.com

 

[AngryKoala]

Anyone have any ancedotal data on JPs thermal fitting and how much it helps improve precision?

 

[MPDS13]

Well, I guess I will just restate what has been said, lol. Good barrel with matched bolt, solid stiff free float handguard, and good ammo. If you are like me. I cannot stand the slop and jiggle between the upper and lower receivers on a precision rifle. I know it may not have a huge impact on the accuracy. But, it feels better and gives me peace of mind. I have been loving the San Tan Tactical receiver sets.

 

[Liberator52]

In addition to all the above listed........ True and glue the receiver. Lap the upper and loctite the barrel extension. Check out you tube if needed.

 

[Greg Langelius *]

I think an accurate upper is the collective result of several smaller issues.

I just finally got out to shoot here in AZ (after 110+ days of 100+ heat), and the AR Stoner sporter billet receiver with integrated handguard makes a difference. It's rigid, period. I lapped and glued the Barrel Extension and Upper together. The barrel is a heavyweight 24" fluted AR Stoner (Liberty?) barrel. There is no perceptible play between the AR Stoner Upper and PSA Classic receiver.

I also believe that a good trigger is a crucial plus over the standard AR trigger, and I installed a moderately economical PSA Nickel-Boron 2-Stage.

The chambering is 6.5 Grendel, brass is Starline, bullet is Speer 90gr TNT, primer is CCI BR-4, and powder is IMR-8208XBR. All of these components, except the BR-4's, are new to me. This is the same rifle that broke its extractor using 120gr SGD's and an excessive load of W-748. The extractor as replaced with the J-P Improved Grendel Extractor, and henceforth all loads will conform to published load limits.

The charge is rounded down to the next .5gr below max as I find that most of my accurate loads are just a few tenths below max. No report on MOA's, too few groups for a representative average, but the rifle does shoot small. Next few groups will be the same load to get a good statistical sample, and then testing of bracket loads will commence to see if any improvement is available. The resulting load is 31.5gr of IMR-8208XBR (31.7gr is max from the Speer Manual), with an estimated 3000ft/sec MV in the 24" barrel with a listed BC of.281. My range altitude is around 4500ft ASL.

In summary, I think the initial results are promising, especially so in the light of the rifle being built with economy in mind, and an effort was made to do the lapping and gluing to see if it is compatible with good performance.

So far, I think it is.

There is another rifle, built on a factory 20" AR Stoner 6.5 Grendel Upper and the same PSA Classic Lower with the same PSA Nickel-Boron 2-Stage Trigger. It comes without the lapping and gluing. Once a reliable benchmark level of accuracy is established, I will lap and glue it to see if that changes anything.

Greg

 

[skyrep]

I think an accurate upper is the collective result of several smaller issues.

I just finally got out to shoot here in AZ (after 110+ days of 100+ heat), and the AR Stoner sporter billet receiver with integrated handguard makes a difference. It's rigid, period. I lapped and glued the Barrel Extension and Upper together. The barrel is a heavyweight 24" fluted AR Stoner (Liberty?) barrel. There is no perceptible play between the AR Stoner Upper and PSA Classic receiver.

I also believe that a good trigger is a crucial plus over the standard AR trigger, and I installed a moderately economical PSA Nickel-Boron 2-Stage.

The chambering is 6.5 Grendel, brass is Starline, bullet is Speer 90gr TNT, primer is CCI BR-4, and powder is IMR-8208XBR. All of these components, except the BR-4's, are new to me. This is the same rifle that broke its extractor using 120gr SGD's and an excessive load of W-748. The extractor as replaced with the J-P Improved Grendel Extractor, and henceforth all loads will conform to published load limits.

The charge is rounded down to the next .5gr below max as I find that most of my accurate loads are just a few tenths below max. No report on MOA's, too few groups for a representative average, but the rifle does shoot small. Next few groups will be the same load to get a good statistical sample, and then testing of bracket loads will commence to see if any improvement is available. The resulting load is 31.5gr of IMR-8208XBR (31.7gr is max from the Speer Manual), with an estimated 3000ft/sec MV in the 24" barrel with a listed BC of.281. My range altitude is around 4500ft ASL.

In summary, I think the initial results are promising, especially so in the light of the rifle being built with economy in mind, and an effort was made to do the lapping and gluing to see if it is compatible with good performance.

So far, I think it is.

There is another rifle, built on a factory 20" AR Stoner 6.5 Grendel Upper and the same PSA Classic Lower with the same PSA Nickel-Boron 2-Stage Trigger. It comes without the lapping and gluing. Once a reliable benchmark level of accuracy is established, I will lap and glue it to see if that changes anything.

Greg

what COAL are you using/recommend. I am presently loading them to 2.180 (0.090 off the lands). I have a 25..6 CZ Varmint MTR in 6.5 Grendel.

 

[Greg Langelius *]

Not as a number. I set my seating stem against the existing Hornady 123SST cartridge. I had bought a bunch of them for loading, but then switched to Speer 120gr Gold Dot. They feed and function fine, but I have no idea what jump to the lands is happening.

Greg

 

[Longhorn in Utah]

Literally just got my White Oak DMR barrel. They are running several months behind on orders. Ordered it July. Now if only I could find some higher grain bullets to actually buy.
Looks like some good quality reloading kit is the goal for 2021.

 

[Greg Langelius *]

Speer 140gr Gold Dot Bullet.

I bought these for my 260 Rem, but Speer lists loads for their 140 Spitzer SP Hot Cor.

Speer Rifle Data.

My preferred bullets are the Speer 90TNT and 120 Gold Dot (SGD).

Greg

 

[Greg Langelius *]

Referring back to your original question, specifying 5.56, the Hornady 75gr HPBT-M will work in a 1:8" twist an 24" barrel, the 75gr ELDM may not. You can use a 20" barrel, but I prefer my pair of 24"s. I imagine the IMI 77 will work similarly.

Handload:

I like Starline brass, but IMI, PPU, and LC work, as do Rem and Win; F/L resized, and any primer crimps removed.
The Hornady 75gr HPBT-Match at 2.260" OAL, and I've prepared some test loads with the 75gr Speer Gold Dot. Not fired yet, but Gold Dots in other chamberings and weights identical to those in pet loads are performing as well or better than the originals.
I test with WSR primers, and when a charge is determined, I then test with a match primer, usually CCI BR-4. Often, the WSR is just as good.
Powder is Varget, 23.5-23.7gr, depending on your barrel's preference.

Greg

 

[benchmstr]

I hand true the lugs and use liquid gasket to bead the barrel to the tried receiver.

I also use only one off barrels that were chambered for me...not chambered in batches for everyone...

All AR's should be free float so that shouldn't have to be mentioned

 

[bigjake83]

I hand true the lugs and use liquid gasket to bead the barrel to the tried receiver.

I also use only one off barrels that were chambered for me...not chambered in batches for everyone...

All AR's should be free float so that shouldn't have to be mentioned

Hand true the Lugs???? Liquid gasket.. like the shot you use on valve covers on an engine????

 

[benchmstr]

Hand true the Lugs???? Liquid gasket.. like the shot you use on valve covers on an engine????

Yeah

 

[benchmstr]

Hand true the Lugs???? Liquid gasket.. like the shot you use on valve covers on an engine????

BROWNELLS AR-15/M16 UPPER RECEIVER LAPPING TOOL | Brownells

Cold-rolled steel lapping tool chucks into a 3/8' hand drill to easily “square” the upper receiver face on your AR-15. Helps ensure precise mating of barrel and receiver for added accuracy. Coat face of receiver with aluminum-oxide lapping compoun...

www.brownells.com

https://www.amazon.com/Permatex-20539-Indian-Shellac-Compound/dp/B0008KLOG6

BROWNELLS LAPPING COMPOUNDS | Brownells

The right abrasive for lapping the final fit between semi-auto slides and frames, rifle bolts and receiver raceways and any other application where a super-close fit or silk-smooth mecha- nism is required. #600 and #800 grit aluminum oxide abrasiv...

www.brownells.com

 

[bigjake83]

Oh....lol

You're talking about truing the FACE OF THE RECEIVER, The only lugs are those on the barrel extension and on your bolt itself and the only thing you can do with them is polish them.

I'd also recommend forgoing the gasket maker and utilize a loctite product. When bedding the receiver and barrel extension the compound needs to be able to harden and gasket maker is flexible rubber-like. Loctite RED 271 works good and allows for reasonably easy barrel removal if you decide to swap it out after you've done this. Green 609 the closest to permanently bonding to the upper receiver.

 

[gulada97]

I got lazy and went with the complete Armalite 18" competition upper. SS barrel, 223 Wylde. Thing shoots 3/4 MOA all day with Lapua 55gr ammo. It's on an Aero Precision lower with Timney trigger. Having a heavy stock helps too, I have one from B-5 systems with adjustable cheek piece.

 

[kjeff91]

What kind of accuracy loss will you find if you bump down to a 16"?

 

[bigjake83]

What kind of accuracy loss will you find if you bump down to a 16"?

Accuracy?? None, Velocity about 30-40fps