6mm Arc Build Questions

[williamagee80]

Good morning everyone. I am looking at building a rifle in 6 ARC and I’m curious what part combinations people who have some time on their builds have had success with. Specifically I’m talking about barrel performance, gas system setup that has been functioning well and buffer tube setup. Thanks and I appreciate any insight!

 

[SalomonQST99]

I built a 6 ARC based around a 22" fluted Shaw barrel. The barrel uses a rifle length gas system with an SA adjustable gas block. Had a carbine length AR-15 buffer and I just tuned for proper brass ejection.

 

[Redlion]

I am interested in recommendations for a build as well.

 

[Ledzep]

I have a 16" build that I'm pretty happy with as a hunting/beater rifle,

Aero upper (no F/A but do whatever makes you happy)
Aero M4e1 lower
Aero handguard
Faxon Match 6mm ARC 16" barrel (YMMV, I think I got lucky with this one it hammers with factory ammo, I know Faxon doesn't always deliver in that regard). Pretty sure it's mid-length
Aero adjustable gas block
Geiselle trigger (3.5lb single stage), standard guts otherwise & magpul grip/stock
Vortex 1-10x razor
Ultra 5

 

[Dogtown]

I've done a 26" rifle +2 gas build, a 16" rifle gas build, and a 20" rifle gas build. All were easy to tune, but what I've learned about these barrels comes down to this:

• 16" is fine for the vast majority of setups and you can still shoot 100-110 class bullets at reasonable velocity
• 26" is too long and not the velocity increase you'd expect
• 20" feels like the sweet spot if you're trying to maximize mass/velocity

 

[stevieb92]

I went with a 20 inch X Caliber barrel (bull profile and rifle gas) on my Mega Arms AR-15 receiver set. Using a JP rifles full mass bcg, SLR Sentry 9 adjustable gas block, LaRue MBT-2S trigger and Vortex Viper PST Gen 1 4-16x50 mrad scope it easily printed sub moa groups with factory Hornady 108 ELD-M.

 

[WestTN2288]

I’m shooting an 18in ballistic advantage barrel, rifle length gas, sa gas block with a Toolcraft BCG. Extremely happy with it. Shooting 108s @2600.

 

[db2000]

Seekins. Geissele Super 42 braided spring, H2 (iirc) buffer, JP HP bolt (which comes headspaced and recommended by) Proof 18” +1 rifle, SA AGB. Almost exclusively suppressed. No issues, very accurate and good velocities.
As mentioned 18-20” is where this cartridge shines. I’ve had good luck with Duramag SS 6 ARC mags.

 

[ut755ln]

Good morning everyone. I am looking at building a rifle in 6 ARC and I’m curious what part combinations people who have some time on their builds have had success with. Specifically I’m talking about barrel performance, gas system setup that has been functioning well and buffer tube setup. Thanks and I appreciate any insight!

I converted a 5.56 LMT to a 6 ARC. I did the barrel swap with D Wilson and bought a Proof stainless barrel. I changed out the bolt face for the 6.5 from JP. I have tried a couple of mags but the only one that has worked flawlessly for me have been the Geissele.

 

[A&8's]

Odin 20”, rifle gas, Odin adjustable block, Anderson lower, TT diamond, JP Enterprise H2 SCS, LuthAR butt stock. “Built” in 2021

Edited to correct date.

 

[db2000]

Odin 20”, rifle gas, Odin adjustable block, Anderson lower, TT diamond, JP Enterprise H2 SCS, LuthAR butt stock. “Built” in 2016-ish


View attachment 8583445

Damn! You beat the DoD building a 6 ARC by like 4 years. And Lowlight will bust a nut when he sees the height on that scope! That’s the future apparently.

 

[A&8's]

Damn! You beat the DoD building a 6 ARC by like 4 years. And Lowlight will bust a nut when he sees the height on that scope! That’s the future apparently.

Well, I have no idea WTF I was thinking of when I said ‘16. Looking at my data book, it reads 5-30-21. lol.

The scope height fits my face comfortably. I’d rather be comfortable than super cool low.

 

[supercorndogs]

18" rifle+1. 22" rifle +2. 16" rifle length gas h2 and h3 buffers in a carbine tube with regular and flatwire springs shooting suppressed. Not problems getting any of them running and adjusted.

 

[Eric_F]

I'm also running a 18" rifle +1" gas. I think it's got an A5H1 buffer, and it's tuned for suppressed but absolutely will not work unsuppressed. I think the performance overlap would be a lot bigger for rifle gas if I was taking the can off a lot.

 

[db2000]

I'm also running a 18" rifle +1" gas. I think it's got an A5H1 buffer, and it's tuned for suppressed but absolutely will not work unsuppressed. I think the performance overlap would be a lot bigger for rifle gas if I was taking the can off a lot.

That’s odd. My +1 runs both. Ejects different angle obviously but runs all the different hand loads I’ve tried. Definitely the factory ammo. I haven’t shot all my load developments unsuppressed though.

 

[Hecouldgoalltheway]

I think if you have a quality adjustable gas block and a JP silent capture spring, (why wouldn't every AR you own have one?), gas systems haven't been an issue for any of the 5 I've assembled.

 

[Eric_F]

I'm sure I could tune it to run unsuppressed, but then with my high back pressure can (Polonium 30) I'd be getting pretty gassed out as the dwell time is pretty tiny it would need a lot of gas. Not a huge deal for me. Picture not really required but why not.

 

[Rob01]

Good morning everyone. I am looking at building a rifle in 6 ARC and I’m curious what part combinations people who have some time on their builds have had success with. Specifically I’m talking about barrel performance, gas system setup that has been functioning well and buffer tube setup. Thanks and I appreciate any insight!

If you want to build that’s great but you can buy and get a good rifle also. I had .223s so just ordered a 22” upper from Grendel Hunter. Got it in about 3 days. Put it on my lower and took it to the range. Ran great and was as accurate as I wanted. Cost me about $800 and I couldn’t be happier. Once I got my wind call down I was hitting 6” and 4” targets at 900 yards. My first time out with some Hornady 108 ammo I shot the below at 100 and 550.

6mm ARC Uppers | Grendel Hunter | The Modern Sporting Rifle

/*! elementor - v3.16.0 - 09-10-2023 */ .elementor-heading-title{padding:0;margin:0;line-height:1}.elementor-widget-heading .elementor-heading-title[class*=elementor-size-]>a{color:inherit;font-size:inherit;line-height:inherit}.elementor-widget-heading...

www.grendelhunter.com

 

[memilanuk]

Seems like different builders are all over the place on the gas system length for 18-20" barrels. Some run 'rifle', some run 'rifle+1', and others (PVA, @bohem ) say 'rifle+2' for all their ARC builds.

Is there a method to the madness that I'm missing?

 

[WestTN2288]

Seems like different builders are all over the place on the gas system length for 18-20" barrels. Some run 'rifle', some run 'rifle+1', and others (PVA, @bohem ) say 'rifle+2' for all their ARC builds.

Is there a method to the madness that I'm missing?

No. They’re just a little pickier than normal calibers. Get an adjustable gas block and don’t worry about

 

[MaximusDecimusMeidius]

I have tried many different configurations and for me this is my favorite. Did not need to run an adjustable gas block either.

 

[ironhiide]

The easy button for 6 Arc that I recommend to friends is:
Aero Enhanced Upper/M4E1 Lower, Aero Enhanced 15" Handguard - but with Aero's junk CS atm, order from a retailer with stock
Rexus Arm's Ultrabolt, Rexus 6 Arc Heavy 18/20" barrel, Rexus Ultrablok set-screw Gas Black ( they dimple the barrels for gas block alignment, so ask for the screws when ordering the barrel)
Buffer system is a plain-Jane Milspec Carbine buffer tube, 3oz Carbine buffer and a Tubb Precision Flatwire spring.
Radian Raptor charging handle to keep gas off your face.
Triggertech Duty Single-stage 3.5lb
Duramag 6.5 Grendel/6 Arc mag with the blue follower.

This build is just at $1k with your choice of stock and grip, minus optic or sighting system.

My personal build with above and 18" barrel gets 2565fps with Hornady Black 105gr ammo.

 

[bohem]

Seems like different builders are all over the place on the gas system length for 18-20" barrels. Some run 'rifle', some run 'rifle+1', and others (PVA, @bohem ) say 'rifle+2' for all their ARC builds.

Is there a method to the madness that I'm missing?

We went +2 on all our gas systems because it tamed things down from the slower powder and higher port pressures. Then when I started playing with the adjustable gas key carriers from RCA I was impressed by how simple it was to set those guns up.

 

[Jsp556]

Aero enhanced build in Kodiak Brown. Rainier Arms “Match” 16” rifle gas melonited barrel.
Maxim bolt in a milspec carrier. Schmid 2 stage trigger. H buffer with standard carbine spring.

It has a Nocpix thermal on it now. Shoots the 105 Black ammo roughly 1.5 moa but shoots the 80gr eldvt under moa right at 2800fps. Haven’t tried anything else.

ETA: No malfunctions to date. It runs great with Duramags.

 

[drwood96]

We went +2 on all our gas systems because it tamed things down from the slower powder and higher port pressures. Then when I started playing with the adjustable gas key carriers from RCA I was impressed by how simple it was to set those guns up.

Which bolt to you include as an option and/or headspace too?

NVM - saw it in the other thread. Rubber city bolts and carriers.

 

[bohem]

Which bolt to you include as an option and/or headspace too?

NVM - saw it in the other thread. Rubber city bolts and carriers.

Yep, I have a number of them and was pleasantly surprised by the fit and finish. @padom turned me onto them and the adjustable key setup last year. He's been using them with great results for a while and when I met Dom a decade ago he was running all JP parts.

 

[memilanuk]

Are there any brands out there that are known to use the type 1 bolts (0.125" deep)?

 

[WeR0206]

Anyone in this thread have any sub $400 6 ARC 18" barrel recommendations? Use case is mainly shooting paper with some potential hunting down the road.

Here's what I'm considering so far after reading through this and some other threads. Half of the below are out of stock so they seem to be slim pickings

• Craddock RTR 6 ARC 18” barrel with muzzle threads (+$60 for headspaced bolt) ($350)
• X-Caliber:
  • Quarter Minute Arms: X-Caliber 18” 6 ARC barrel (with gas tube & muzzle threads) (get with headspaced JP bolt assembly for +$155) ($370) ($525 with JP Bolt Assembly)
  • Direct: X-Caliber Custom AR Barrel 6 ARC 18” (add Rubber City headspaced BCG for +$200) (with muzzle threads) ($372)
• Patriot Valley Arms - Osprey 18” 6 ARC barrel with rifle +2 ($399) (add headspaced Rubber City bolt for $125)
• Shaw 18” HBAR rifle length barrel ($200)
• Rexus 18” 6 ARC Heavy profile Rifle Length Chrome Moly Nitrided Barrel ($165)

RTR's are out of stock. Shaw is available at Optics Planet.

 

[memilanuk]

I'm in a similar spot... you might add the following to the list: 20" Precision Firearms (formerly Samurai)

 

[Jdowns0415]

Anyone in this thread have any sub $400 6 ARC 18" barrel recommendations? Use case is mainly shooting paper with some potential hunting down the road.

Here's what I'm considering so far after reading through this and some other threads. Half of the below are out of stock so they seem to be slim pickings

• Craddock RTR 6 ARC 18” barrel with muzzle threads (+$60 for headspaced bolt) ($350)
• X-Caliber:
  • Quarter Minute Arms: X-Caliber 18” 6 ARC barrel (with gas tube & muzzle threads) (get with headspaced JP bolt assembly for +$155) ($370) ($525 with JP Bolt Assembly)
  • Direct: X-Caliber Custom AR Barrel 6 ARC 18” (add Rubber City headspaced BCG for +$200) (with muzzle threads) ($372)
• Patriot Valley Arms - Osprey 18” 6 ARC barrel with rifle +2 ($399) (add headspaced Rubber City bolt for $125)
• Shaw 18” HBAR rifle length barrel ($200)
• Rexus 18” 6 ARC Heavy profile Rifle Length Chrome Moly Nitrided Barrel ($165)

RTR's are out of stock. Shaw is available at Optics Planet.

Get the satern/liberty or from Grendel Hunter. Someone recommended it to me in the 6mm arc thread because my Odin just flat out wouldn’t shoot and had issues from the factory they never fixed. Got a 20 inch barrel from Grendel Hunter. Loaded up some 105 Berger VLD targets at 2.295 COAL and 29gr of lever with a CCI450, went 10/10 at 800 on a 1MOA plate after I zeroed it. I shot my 10 shot load development group standing leaning on a bench with a bag and all 10 shots were touching in a vertical line. The barrels are cheap and 200 rounds in its made me more than happy.

 

[WeR0206]

I'm in a similar spot... you might add the following to the list: 20" Precision Firearms (formerly Samurai)

Good find. I'm tempted to go for the Shaw...with coupon code at OP it can be had for around $187.

Shaw AR-15 6 ARC Threaded Barrel Up to 10% Off w/ Free S&H — 6 models

Shop Shaw AR-15 6 ARC Threaded Barrel | Up to 10% Off 4 Star Rating on 1 Review for Shaw AR-15 6 ARC Threaded Barrel + Free Shipping over $49.

www.opticsplanet.com

If I didn't have a wife/kids I'd be all over the Osprey but I already have a 308 shouldered barrel from NSS on the way and the wifey is sure to be like WTF how many barrels do you need??

 

[WeR0206]

Get the satern/liberty or from Grendel Hunter. Someone recommended it to me in the 6mm arc thread because my Odin just flat out wouldn’t shoot and had issues from the factory they never fixed. Got a 20 inch barrel from Grendel Hunter. Loaded up some 105 Berger VLD targets at 2.295 COAL and 29gr of lever with a CCI450, went 10/10 at 800 on a 1MOA plate after I zeroed it. I shot my 10 shot load development group standing leaning on a bench with a bag and all 10 shots were touching in a vertical line. The barrels are cheap and 200 rounds in its made me more than happy.

2.295" COAL? Are you shooting in a bolt gun? For gas gun we're capped at 2.260"

I was giving the Liberty 18" a hard look but not sure I like an 18" ARC barrel having a mid-length gas system. Would prefer at least rifle length.

 

[Jdowns0415]

2.295" COAL? Are you shooting in a bolt gun? For gas gun we're capped at 2.260"

I was giving the Liberty 18" a hard look but not sure I like an 18" ARC barrel having a mid-length gas system. Would prefer at least rifle length.

ASC ARC mags fit that COAL. when I measured my barrels Jam with hornady brass and those VLD’s it was longer than the mag so I just got it long as possible but still feed reliably. I know hornady bullets are loaded shorter for factory stuff.

 

[FromMyColdDeadHand]

Well, got most of the parts. I didn’t think that if I bought a JP Enhanced Bolt and a bolt carrier that neither would have a firing pin, bolt cam pin and firing pin retainer…

Anyways:
Vltor upper
Proof 20 inch 6ARC 1:7.5
Aero precision adjustable gas block
Little bastard 3 comp (replaced JP)
GEISSELE Mk18 16.5 inch rail
Noveske lower that I’ve had in my safe for 15 years
GEISSELE Trigger G2S
Magpul PRS lite
JP heavy adjustable BCG
JP captured spring buffer
Seekins LPK (was missing the safety detent and spring??? WTFudge
MDT grip
Got the bedding compound, but the barrel was pretty tight, so I skipped it.
Strike industries AMbi safety was unusable. Would hardly turn, used the Seekins safety that I didn’t realize was part of the kit. Much better, as in it actually turns.

 

[ut755ln]

Well, got most of the parts. I didn’t think that if I bought a JP Enhanced Bolt and a bolt carrier that neither would have a firing pin, bolt cam pin and firing pin retainer…

 

[FromMyColdDeadHand]

Oddly enough, my go-to for parts was Optics Planet, but they have so many options, I sometimes didn’t get the differences. Plus they sometimes have the same thing (or what seems to be) the same thing under different codes.

Got it together last night. Hope to get to the range today to at least break in the barrel and gas system.

 

[WeR0206]

Oddly enough, my go-to for parts was Optics Planet, but they have so many options, I sometimes didn’t get the differences. Plus they sometimes have the same thing (or what seems to be) the same thing under different codes.

Got it together last night. Hope to get to the range today to at least break in the barrel and gas system.


View attachment 8611109

Very nice! Are the vltor uppers thermo fit or can you just slide the barrel on?

 

[WeR0206]

Good find. I'm tempted to go for the Shaw...with coupon code at OP it can be had for around $187.

Shaw AR-15 6 ARC Threaded Barrel Up to 10% Off w/ Free S&H — 6 models

Shop Shaw AR-15 6 ARC Threaded Barrel | Up to 10% Off 4 Star Rating on 1 Review for Shaw AR-15 6 ARC Threaded Barrel + Free Shipping over $49.

www.opticsplanet.com

If I didn't have a wife/kids I'd be all over the Osprey but I already have a 308 shouldered barrel from NSS on the way and the wifey is sure to be like WTF how many barrels do you need??

After giving it some more thought Im gonna save up for a few months (possibly wait for holiday sale) and get the below Osprey from PVA. @bohem I see you recommend clamp on style gas blocks, any particular brand seem to fit/work well on the ospreys?

• Patriot Valley Arms - Osprey 18” 6 ARC barrel with rifle +2 ($399) (add headspaced Rubber City bolt for $125)

Thanks

 

[FromMyColdDeadHand]

Very nice! Are the vltor uppers thermo fit or can you just slide the barrel on?

I’d say non-thermo from what I read and with my Proof barrel. I didn’t heat it up and it didn’t seem to need it. If anything, it seems teh Proof barrel is ever-so-slightly tapered to be a bit bigger towards the muzzle? As I was test fitting it, I’d get to about the last 1/4 inch and it would get tight. I thought I wouldn’t use the bedding since it wasn’t loose at all, and I could do it later if I really wanted to. Since I was just playing around I didn’t press very hard. When it came time to install it, I had to press a bit hard to get it to totally seat.

 

[WeR0206]

I’d say non-thermo from what I read and with my Proof barrel. I didn’t heat it up and it didn’t seem to need it. If anything, it seems the Proof barrel is ever-so-slightly tapered to be a bit bigger towards the muzzle? As I was test fitting it, I’d get to about the last 1/4 inch and it would get tight. I thought I wouldn’t use the bedding since it wasn’t loose at all, and I could do it later if I really wanted to. Since I was just playing around I didn’t press very hard. When it came time to install it, I had to press a bit hard to get it to totally seat.

Ok thanks. For my build I think I'm going to go with a BCM Blem Upper...the price is just too good. I'll hit it with a heat gun for a min or two then slide barrel on, then hand tighten the nut, let it cool, then grease the threads and torque the nut down.

Minus the barrel here's what I'm looking at for my build so far...open to any tweaks/suggestions

• Base build:
  • Yankee Hill Phantom 7.62 Flash Hider ($40) or EFAB 7.62 hybrid muzzle break/flash hider ($162)
  • BCM Gas Block ($35)
  • BCM Rifle Length Gas Tubes ($16)
  • BCM Blem Upper ($80) + Wheeler Lapping tool ($25)
  • Rubber City Armory BCG ($199) or SOLGW 6 ARC BCG ($237)
  • KAK 15” handguard ($115) or Midwest 14” Combat rail ($151)
  • KAK Mil-spec charging handle ($18)
  • Total is $528

 

[memilanuk]

@bohem I see you recommend clamp on style gas blocks, any particular brand seem to fit/work well on the ospreys?

I'm very interested in this as well. The last couple AGB I've used I torqued them down to what I thought was pretty damn snug, but I had gas leakage all over the place. To the point I'm seriously considering that AGC that PVA offers with the matched bolt.

 

[FromMyColdDeadHand]

A Blemished BCM upper is hard to pass up. I wanted this to be a ‘nice’ looking rifle, other wise I think that you got the right idea.

I think that any build I’m going to do in the future is going to have a variable gas block- unless it is a pure SHTF type gun. Just too many good things can come out of it- and with suppressors getting easier (or at least faster) to get- and are pretty advanced now. The ability to go can or no- and not choke on the blowback. I was sold on them with my First JP build. LMOS/Variable gas is so SWEET and smooth firing, especially with a good brake. Plus when the gas is dialed in the gun shoots cleaner.

I was watching the first half of the 9-hole review of the Gieselle GFR… hoping for performance something like that.