6mm ARC extremely dirty?

[Obi-WanKannoli]

So, quick run down on the relevant parts of my setup:
- 14.5 inch Proof 6mm ARC Barrel, Intermediate Length Gas
- Superlative Arms bleed off gas block, 16 clicks (in bleed off) to run both suppressed and unsuppressed.
- Noveske Marked RCA BCG
- Geissele Super42 with H2 Weight


Gun is 100% reliable, absolutely zero malfunctions thus far. Exceptional accuracy, I truly believe the gun has 1/2 MOA in it if the guy behind it is up to snuff. Everything internally is 100% aligned. BCG, Bolt, Bartel extension, Gas key / tube, etc do not bind, snag, or anything.

All that said, this thing gets completely caked in carbon after about 50 rounds, see below:

Thoughts, experiences? I did reach out to Hornady today.

 

[Shoots 700's]

Factory or handloads?

 

[Obi-WanKannoli]

Factory or handloads?

Factory 103 ELDX

 

[Longshot231]

I have to ask the obvious; are you running it suppressed?

 

[Obi-WanKannoli]

I have to ask the obvious; are you running it suppressed?

Of course, I'm not an animal.

Still a lot of carbon for 50 rounds, plus I am using the gas block in the bleed off setting.

 

[Longshot231]

Of course, I'm not an animal.

Still a lot of carbon for 50 rounds, plus I am using the gas block in the bleed off setting.

Pardon me for asking this one. Does it foul this bad when unsuppressed?

 

[Shoots 700's]

What suppressor?

 

[Obi-WanKannoli]

Pardon me for asking this one. Does it foul this bad when unsuppressed?

Yeah, doesn't seem to produce any appreciable difference, I did check that two weeks ago.

What suppressor?

I have been running my form 1 on this. It's a very a low back pressure ~6.5 inch can. Co-axial porting in the skirts, etc.

 

[cas6969]

1965 here we come!


No, no, no...

 

[loclass]

I find the same filth with my 6 arc. Mine is a 22" CLE chambered Criterion with rifle +1 gas. Shooting with my Omega 300 it is the filthiest gas gun I own by far. I've been using 105 and 108 factory ammo for the first 100 rounds. I'm interested to see if that changes as I work up my own loads.

 

[Longshot231]

My thought is this. Find someone that you don't like that has another AR-15 in 6mm ARC and ask them to try the factory ammo that you are using.

Then see if it fouls up their rifle as bad as your gun. Then when they bitch at you about it, just tell them to quit complaining as you gave them free ammo.

This will eliminate any possibility that your rifle is at fault.

Based on what @loclass said, it sounds like an ammunition problem.

Does any other manufacturer besides Hornady make 6mm ARC? If so, it might be worth a try to experiment with it.

 

[Olen_4504]

I found the factory 108g to be very dirty suppressed.

The 103g seems to be a little less dirty.

 

[hlee]

What issue is the carbon causing? Reduced reliability? Accuracy degradation?

 

[TonyTheTiger]

My 6mm Grendel is the dirtiest gun I have. 8208XBR or CFE223 powder. Not a problem in any way. Just keep dumping motor oil in.

 

[Vynz]

Given the length of the barrel, would it be opening earlier causing more fouling?

 

[BELLYCRAWL]

Your pics look clean compared to mine. My 6ARC is by far the dirtiest gun I own. 18” BA, rifle gas. Omega 300…I’m not an animal either.

 

[camotoe]

What part of, "it shits where it eats" do you not understand.

 

[Obi-WanKannoli]

What part of, "it shits where it eats" do you not understand.

I would say mostly that it's shitting a whole lot more than it's eating.

 

[RMB]

I shoot a 6MM AR and it is dirty after about 100 to 120 rounds. Of all the powders I have tried 8208 seems the "cleanest". BLC2 is the worst. I shoot is suppressed 90% of the time.

 

[SupressYourself]

My 6mm Grendel is also quite dirty suppressed, but not nearly that bad. I think there's multiple factors here:
1. Short barrel is not burning all the powder.
2. The powder they use is on the dirtier side. -- Most of the powders that run the highest velocities in Grendel sized cases like CFE223 and LeverRevolution tend to be dirty.
3. The suppressor: back pressure shoots shit back down the barrel upon ejection.
4. Looks like you may be running it pretty wet, and some of the carbon and unburnt powder is sticking to whatever you're using instead of flying out the ejection port.

There's not going to be a great solution.
You could drop the suppressor if you're an unwashed heathen, or you could hand load using a powder that will give you are more complete and / or cleaner burn. I would also experiment with different lubes. I like Hornady One Shot in my ARs.

 

[ReaperDriver]

So, quick run down on the relevant parts of my setup:
- 14.5 inch Proof 6mm ARC Barrel, Intermediate Length Gas
- Superlative Arms bleed off gas block, 16 clicks (in bleed off) to run both suppressed and unsuppressed.
- Noveske Marked RCA BCG
- Geissele Super42 with H2 Weight


Gun is 100% reliable, absolutely zero malfunctions thus far. Exceptional accuracy, I truly believe the gun has 1/2 MOA in it if the guy behind it is up to snuff. Everything internally is 100% aligned. BCG, Bolt, Bartel extension, Gas key / tube, etc do not bind, snag, or anything.

All that said, this thing gets completely caked in carbon after about 50 rounds, see below:

View attachment 7900049View attachment 7900054View attachment 7900051View attachment 7900052View attachment 7900053

Thoughts, experiences? I did reach out to Hornady today.

Holy crap!!! I did a carbine course with well over 1500 rounds (probably 2K) over a weekend with no cleaning and it wasn't a quarter as dirty as that.

 

[Vynz]

Are all of you with the super dirty rifles using 6ARC and 6.5 Grendel as general purpose high volume carbines/rifles? I always thought of these as semi-precision cartridges only since in my experience the magazine reliability hasn’t been there.

 

[TonyTheTiger]

Are all of you with the super dirty rifles using 6ARC and 6.5 Grendel as general purpose high volume carbines/rifles? I always thought of these as semi-precision cartridges only since in my experience the magazine reliability hasn’t been there.

Hell no. Not because of mag reliability, but mag capacity, cost and a big waste of extra ballistic horsepower make it sound silly.

 

[Pjdardis1986]

It's a dirty round. Leverevolution is what hornady using in factory ammo. It's a great power for an extra 100-200fps in velocity but it's very dirty

 

[Pjdardis1986]

It's a dirty round. Leverevolution is what hornady using in factory ammo. It's a great power for an extra 100-200fps in velocity but it's very dirty

Powder*

 

[357Max]

Powder*

I love the smell of Lever in the morning. The factory 108 doesn't smell like my Lever loads. You sure that's what they're using?

Lever is a pretty filthy powder. Also my 108 Lever loads are 115fps faster than the factory loads.

 

[hlee]

Hornady doesn’t use “canister powders” in their loaded ammunition, according to their CS.

 

[newageroman]

I ran a lot of rounds of mostly lever and at around 1,500 I had cycling issues. Replaced gas tube (clogged) fixed. I'm an unwashed hethen though. I will be looking for a cleaner burning plinker powder.

 

[h2oskiier30]

It's just an inherently dirty round, IMO.

I built two different 6mmARC rifles. Both shoot dirty as hell. So, I decided I'd convert one to piston rather than DI, figuring most of the carbon blowback was coming from the gas tube...wrong. Piston conversion rifle still runs dirty as can be. Yes, suppressed, of course.