I'm in the process of building a 6mm ARC upper to be used with my A2 lower with standard GI A2 Buttstock and rifle length gas tube/spring. Right now I've got some of the parts

1. Aero Precision M4E1 enhanced upper W/O forward assist
2. Aero Precision 15" Quantum handguard
3. Aero Precision 6.5 Grendel/6mm ARC BCG
4. Aero Precision Breach charging handle
5. Ballistic Advantage 20" 6mm ARC DMR Rifle Length 1/7 SS Premium Black series barrel
6. Aero Precision Low Profile Gas Block
7. Rifle length Gas tube.

Can't find any 6mm ARC muzzle brake. Does anybody have any suggestions also I want to lower the anger and frustration level to the bare minimum so I'm looking for any suggestions on how to do this without any glitches.

Please give my any suggestions and advice on building this upper.

Thanks.

Use any 5/8 x 24 brake.

Ammo costs are high and brass to reload is nonexistent. My brass has been on back order about two years.

You can form 6.5G brass but I've read mixed results so I've never tried it.

I have the 18" BA barrel and it shoots very well, fun cartridge that kills hogs and coyotes quite effectively.

i used the VG6 65 brake which is for 6.5CM, figured close enough, better than a 7.62 brake.  Area419 has a 6mm-specific brake, 5/8-24 thread.  pricey, though.

I’ve found Hornady 6mm ARC 140gr  BTHP Match for $31.99 a box which doesn’t seem that bad. Any thoughts on that?

No way. The heaviest factory loaded bullet in this caliber is the 108 ELD-M. Whatever you're looking at isn't 6mm arc.

Any 30 cal, 5/8×24 muzzle device will work just fine. What attributes do you want in selecting an MD? Max recoil mitigation, flash suppression, suppressor compatibility, etc?

Local gun shop or shipped?

Hornady makes a 105gr HPBT Match round that sells for about that. All I've used factory wise is the 108gr ELD Match in order to slowly acquire brass.

Personally, $32/box is damn high BUT that's the current times we are in. If you can score that locally w/o paying shipping then I suppose whether or not it's a "good price" depends on what you're willing to pay to shoot the cartridge.

I'm sitting on PLENTY of primers, various projectiles, and various powders, just wish I had got some factory brass when it first came out.

I haven't heard anything bad about Ballistic Advantage, so don't think I'm bagging on them.  I simply don't have experience with them.

That said, specifically with the 6mm ARC I've had multiple Proof Research barrels and Compass Lake Engineering Bartleins which have all produced excellent results.

Otherwise everything looks solid.  If the barrel doesn't require heat to the upper to fit, I very strongly suggest bedding it or shimming it.  I used to be skeptical of the process but watched my groups (20 shot groups) almost cut in half with the exact same ammo.


ETA: As far as ammo, I've had the best luck with 108 ELD-M and 103 ELD-X factory.  The 105 "Black" cycles well but hasn't grouped as tight for me. YMMV.

Can anyone speak to a buffer setup for the ARC?  I know op is using a 20”, and rifle gas.  What about 16”?  Looks like CLE offers a douglas 15.1 (NSW) / 16.1 Recce, both with mid gas.  Do these need H3s?

I am using a carbine buffer and spring along with a MagPul PRS Lite stock with my 18" Odin Works barrel. It came with an adjustable gas block but I haven't had to adjust it from factory using Hornady ammo.

Use whatever flavor 6.5mm brake you like


I went with a V6G

Ammo shouldn’t run more than a $1.20 per or so.