Super dirty brass suppressed AR10 platform

[gf99-99]

I am a long time AR15 owner but have never really dabbled in the larger formats until now. I had an itch to build a 6.5 creedmoor gasser so I finally got around to get it up and running. Took it to the range the other day to sight it in and just see how it runs and everything seems great except the brass is absolutely filthy, with out exaggerating almost the entire casing is black. Is this normal for a AR10 in 6.5??

I have lots of ar15 platforms in 5.56, 300blk, 9mm, .22 and have cans for all of them, yeah the brass gets dirt but this seems excessive. Heck even my suppressed 22 uppers are not this dirty and I didn't think anything could be more dirty then a .22

Now I will admit I was just shooting cheap $20/bx ammo so my only thought is maybe that is the issue??? it was S&B 6.5 creedmoor 142gr hpbt

Firing component are:
Enticer L Ti can
20" BSF barrel
Superlative adj. gas block; I have it adjust so it throws brass pretty much at 3:30-4'oclock, tried to get it undergasses as much as possible.
generic gas tube (don't remember)
JP FMOS bolt carrier
cheapy Aero buffer & spring. I think Aero calls it the "308 rifle buffer" and "308 rifle spring"

I might try and undergas it a little more but I already am almost throwing brass to 4'o clock already and I still want the thing to cycle.

Any thoughts or suggestions, or am I just over thinking it?

 

[Weldor]

They run dirty, you can try a adjustable gas key might help. I run adjustable bolock and key. Some powders are just dirtier than others.

 

[czgunner]

The soot on cases is less about the gas coming into the BCG and more about the suppressor keeping gas in the barrel during unlocking from what I understand. I have a riflespeed on my 308 Stag L and I can't say it has done anything for sooty cases, rather it helps to keep gas out of my face and softens recoil.

Sent from my Pixel 3 using Tapatalk

 

[gf99-99]

Ok thanks for the feed back I guess I might be making mountains out of mole hills.

It's just I have never seen brass come out that dirty be for so it was a little be of a surprise to me. But like I mentioned earlier gun shoot great and cycles perfect so probably not much to worry about.

 

[RockAndSage]

Trying different ammo would be the first thing I'd do, before making any other adjustments. Depending on your application, reliability is usually the most paramount issue, followed by accuracy, so if it's running fine and you're getting acceptable accuracy, it'd be advisable to leave the gun as-is. Trying different loads from different companies will probably turn up some cleaner burning options.

 

[waspocrew]

My 6 ARC brass shooting suppressed is absolutely filthy. I've just chalked it up to the suppressor and never worried about it.

 

[The Harbor Master]

Got pics of the dirty brass? My suppressed 5.56 brass is startling dirty.

 

[gf99-99]

Trying different ammo would be the first thing I'd do, before making any other adjustments. Depending on your application, reliability is usually the most paramount issue, followed by accuracy, so if it's running fine and you're getting acceptable accuracy, it'd be advisable to leave the gun as-is. Trying different loads from different companies will probably turn up some cleaner burning options.

Yeah that was originally my first thought, that's why I made to sure to note that I was just shooting cheap S&B box ammo. I just can't justify shooting $40-$50 a box ammo out of a gas gun just for fun. But ill check around for some more cheap 6.5. I think my local shop has some Winchester white box special, and Aguila for $20 a box as well. Might be worth a try.

My 6 ARC brass shooting suppressed is absolutely filthy. I've just chalked it up to the suppressor and never worried about it.

THanks for the info, glad I am not the only one.

Got pics of the dirty brass? My suppressed 5.56 brass is startling dirty.

Ill see if I can remember to snap some next time I have it out. But I will say my 5.56 brass is usually pretty normal looking, mostly shooting 10.5" or 12.5" uppers out of an RC2 can.

 

[justin davis]

Welcome to suppressed semi autos. They make brass super dirty! Normal thing in my opinion

 

[mtnkid85]

Ive wondered if a heavier buffer would help with this by keeping the bolt closed longer and giving the gas more time to exit through the muzzle before it unlocked.

 

[Loo.wii]

It’s normal
There’s a company that makes a bleedable bolt carrier. It works well but you’ll always have dirty brass. Honestly it may be in your best interest to run a bit more gassy as a measure to maintain reliability by evacuating debris.

 

[RockAndSage]

Ive wondered if a heavier buffer would help with this by keeping the bolt closed longer and giving the gas more time to exit through the muzzle before it unlocked.

The concept you're thinking of is "dwell time", and in a blowback gun like a Thompson or an Uzi, heavy springs and heavy bolts are exactly what increase dwell time. In an AR though, it doesn't work that way - the gas is more or less calibrated to hurl the bolt-carrier group back at a certain velocity, and if you add mass or spring power all it does is cause varying levels of short-stroking, leading to failures to eject or failures to fully strip off the next cartridge out of the magazine and failure to fully chamber it. Essentially, making it undergassed (that's one of your diagnostic points for a gun being undergassed, too heavily sprung, or too heavy of a buffer, btw - short-stroking). The bolt would still unlock at the same rate, however.

What largely governs dwell time is the length and geometry of the cam pin's channel at the front of the bolt carrier. Stretch that out and alter the cam path a bit, and you can keep the bolt locked just long enough with a suppressed gun to get it the bore more effectively de-pressurized. This is exactly what LMT did with their Enhanced Bolt Carrier.

 

[khuber84]

My 22arc brass suppressed is filthy too, run one extra click on adj gas block that locks back on empty mag.