I am wanting to finish a medium range AR-15 in 6mm ARC. Leaning towards getting a custom Bartlein barrel spun up. Might shoot suppressed with a TBAC 30CB9. Looking for recommendations on barrel length, profile, etc. What is working well for you?
Recommendations for 6mm ARC barrel
- Thread starter Lone star Shooter
- Start date
I'm the opposite. I would not go shorter than 18". This is a bullet that gets it effect from moving fast - you don't have the mass of heavier calibers.
I have 20" gasser and its getting 105s moving at 2600. That isn't hot, in my book. Think better powders might get 105 to 2700, which is materially better.
I did up a little table evaluating the 105gr Berger at 700yds at various MVs. I benchmarked all the results to 2700. So you can see, cutting this cartridge down to 2500fps (the MV you likely get at under 18") you are really handicapping this thing.
Now if all your shooting is under 700yds, maybe this doesn't matter to you.
I have 20" gasser and its getting 105s moving at 2600. That isn't hot, in my book. Think better powders might get 105 to 2700, which is materially better.
I did up a little table evaluating the 105gr Berger at 700yds at various MVs. I benchmarked all the results to 2700. So you can see, cutting this cartridge down to 2500fps (the MV you likely get at under 18") you are really handicapping this thing.
Now if all your shooting is under 700yds, maybe this doesn't matter to you.
MV fps of 105gr | drop at 700 | wind at 700 | Energy at 700 |
2500 | 20% | 13% | -18% |
2600 | 9% | 6% | -9% |
2700 | 0% | 0% | 0% |
2800 | -8% | -6% | 10% |
3050 (my 6x47L bolt gun load) | -26% | -17% | 35% |
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On profile, I have a 0.875" gas port and love it. It is wicked precise yet still not weighing a ton. It is super low recoil, like a dream, feels like a 223Rem.
Craddock did my barrel and I would recommend him. He has a nice product offering going with a 6ARC barrel from your choice of three different barrel makers. His line is long however.
Craddock did my barrel and I would recommend him. He has a nice product offering going with a 6ARC barrel from your choice of three different barrel makers. His line is long however.
What length did you go with? I was thinking 20” or 22”, .875” gas block, rifle +2” gas system.
Berger recommends 1:8” twist for their 105 gr hybrid target bullets. Any reason to go with a faster 1:7.5” twist?
Cracdock is one of the gunsmiths I am considering.
I have 20". Would go 22" if I had redo. 2" = 50fps which is a good bit of kinetic energy and you will not know the difference between a 20" and a 22".
I have 0.875" gas block, rifle +2 gas. Recoil so nice.
Twist: 8twist or faster. Don't sweat 7 or 8 twist. Either gets job done w/o major impact.
Agree that Craddock does well with barrels. I am super curious and a learner on the ARC. I have heard so many good things, and I am a barrel and scope nerd, but never looked at the ARC. My instincts would be to get the projectile moving as fast as possible, and my knowledge of 5.56mm and 7.62mm guns and barrels would make me think that 20" to 22" would be ideal. But, why such a wide journal for the gas port? If you want to run a long barrel, I would think I would want to keep it thinner (less weight) and run 0.75" journal and keep taper from the breach to the gas port.
I've had good luck with my Proof 18" CFW 6mm ARC barrel shooting the Hornady 105 BTHP (2689 FPS):
Here's my first five at 100 yards the other day:
Wish I could do that every time ........
I also have in stock a couple of 16" Proof CFW barrels I haven't had the chance to try yet. There's a 16" Bartlein by Craddock here ready to go, too.
Here's my first five at 100 yards the other day:
Wish I could do that every time ........
I also have in stock a couple of 16" Proof CFW barrels I haven't had the chance to try yet. There's a 16" Bartlein by Craddock here ready to go, too.
that is good performance all around.
@longshot2000
on your question why I went 0.875" at the gas port. I'm not a nerd on this stuff, so I'm just 'speculating', but my answer is I have found 0.875" isn't too much heavier than a 0.75" AND, more importantly for me, they seem to hold precision better than 0.75" after several rds thru the tube. I find the 0.75"s precision opens up badly after a dozen or so rounds, whereas you have maybe 5 or 6 more rds of tight impacts with a 0.875.
Is this reality or not? No idea, but at least that is the case in my brain.
Id go with as long a barrel as you can possibly feet comfortable with(depends on application/use), for the MV advantage., along with .875 gas block as said. Light barrels can be astoundingly accurate, but heavier/thicker is mostly always better when hoping for max precision...JMO!
can you explain to me the reason for adding 2 inches to a rifle length gas system?
I just bought mine on here from Front Range Precision, he had a few in stock and was super easy to work with!
Keeps the port to muzzle distance the same. This is an issue of bolt timing. When you increase port to muzzle distance, you end up with more time the bullet is in the barrel past the gas port. This does tend to increase port pressure, but even worse, it allows the rifle to start cycling before the chamber pressure has dropped to design intent.
so you run a longer gas system, and get your cycle timing back in order. Makes life easier on the brass, easier on the rifle, and ultimately, easier on you, as less gas will be coming back into the rifle from a still pressurized chamber/barrel.
I am maybe around 3 or so weeks from getting my barrel from McGowan.
I am the reigning grand champion of of over analysis and I went with a 24" barrel with a 1:7 twist. While you can stabilize bullets with less twist it just depends on what you want to be doing. I personally knew that I was going to shoot heavy bullets and I wanted to keep the option of shooting 115 grain bullets possibly on the table.
Basically though if you figure up your RPM's of your bullet (based on common velocities achieved with your cartridge) so long as the RPM's are below 300,000 you are good to go. I chose the extra twist because I was erring on the heavy side. I pretty much will never shoot lightweight bullets I don't think.
The 1:8 can stabilize all of the lighter end bullets and probably a fair amount of the longer heavier ones, but there are limitations. The 1:7.5 gives a bit of wiggle room. The 1:7 choice should work just fine as well but gives a bit more leeway for the heavies. There are 115 grain DTACs, 112 grain Match Burners, 109 grain, 110 grain, and probably a bunch more heavies that are available in 6mm.
A traditional .243 has twists between 1:8 and 1:10 but seeing how this is 2021 and there are constantly evolving high BC bullets that change the landscape of where the goal line is at.
That's why I went with 1:7... so I can have more wiggle room and still be well under the 300,000 RPM threshold.
Threads like this are what I really appreciate about this forum and online community.
Me too. The problem is that it often leads to me spending money on something that I had no idea I needed!
Yes, I am. It's a good quality upper.
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I've had really good luck with Shilen match barrels spun up by Mike Milli at Dedicated Technologies. Most have been in 223, but I had him do this barrel in 6 ARC. 20" medium contour, rifle length gas (.875 gas block), fluted and threaded. Turnaround was about 9 months, but worth the wait.
Took it out Monday for the first time and after 20 rounds of factory Hornady Match 108 ELDM, cleaned the barrel and decided to shoot a 5 round group. Despite the first round clean bore flier, I was pretty happy. I think it has potential.
Took it out Monday for the first time and after 20 rounds of factory Hornady Match 108 ELDM, cleaned the barrel and decided to shoot a 5 round group. Despite the first round clean bore flier, I was pretty happy. I think it has potential.
I just ordered a Compass Lake Douglas in 20". Looking forward to it. Hope it is a shooter.
I just received my 22 inch Douglas which was spun up by Kenneth at Desert precision. Still got to get the upper together before I can test it out.
@NH4X. The numbered 5th shot was actually the first shot out of a clean barrel. I numbered them that way so I could remove that shot out of the group to see what the 4 shot group measured. I tried numbering in shot order, but I couldn't find a way to remove the flier without Ballistic-X removing the shots in order. This is the first time I've used Ballistic-X so there may be a way to do this, I'm just not aware.
How is the recoil since you don’t have a muzzle brake? I know it’s subjective in all, I run all my .223 guns without a brake. I’m on the fence about threading the muzzle for a 6mm ARC build. I’d prefer not to, one less thing to potentially effect accuracy. But I want a rifle that’s comfortable to shoot for my young sons too. ThxI've had really good luck with Shilen match barrels spun up by Mike Milli at Dedicated Technologies. Most have been in 223, but I had him do this barrel in 6 ARC. 20" medium contour, rifle length gas (.875 gas block), fluted and threaded. Turnaround was about 9 months, but worth the wait.
Took it out Monday for the first time and after 20 rounds of factory Hornady Match 108 ELDM, cleaned the barrel and decided to shoot a 5 round group. Despite the first round clean bore flier, I was pretty happy. I think it has potential.
I've not put a break on it yet to see what the recoil is like, but without a break I really couldn't tell much difference from an un-breaked 223.
I started my son, when he was seven, on a 223 that DTech built. I'd not have hesitated to let him shoot the ARC.
Yote, another couple questions I’m getting ready to order a barrel from Dtech. What rifling, how many grooves, twist rate and what’s the gas length standard rifle or plus 1”, 2”? Now that you’ve had it a while any thing you would do different? Also how is it on the brass and are you using Mike’s non-adjustable gas block? He is definitely a deal for the quality received. Thank you
Westcoast,
I can only answer a couple of your questions, as I didn't get specifics to the level you are asking. My barrel is a 1:7 twist, standard rifle length gas using a standard low pro block from aero precision. I'm completely happy with the rifle as I built it and wouldn't change a thing. I've not noticed any marks on the brass or primer deformation in the factory ammo I've been using.
Give Mike a call and he can answer your questions better than I can.
I wouldn't get the WC with that mid-length gas system. I was looking forward to getting a WC ARC barrel till they came out with RLGS and MLGS and immediately cancelled the former. I wound up ordering an 18" X-Caliber lightweight w/RLGS when they had a sale going for just a little more, and love it.
Awesome thank you. Seems like a very straight forward accurate build that’s easy on brass, perfect. I’ll talk to Mike and get a barrel on order.
Rainier would certainly be my choice. At least in that price range.
Along w/ Criterion(Rainier UM's are Criterion anyway..), and WOA if they offer 6ARC...
