Rifle:
14.5" Nitride Barrel with NiB BCG
Carbine Gas with Syrac Adjustable Gas Block
Slash's CAR10 Heavy Buffer & JP 308 Carbine Spring
AAC 762-SDN-6 Suppressor

So I got the rifle out to tune the gas system and used 155gr Amax unsupressed. I dialed in the gas block WITHOUT the suppressor at the lowest setting that would still allow the bolt to lock back on an empty magazine - figuring that adding the suppressor will only aid in positive cycling with the extra back pressure & gas. It only took about 5 shots to get the gas block where it needed to be so I threw on the suppressor and it definitely cycled with a bit more charisma... for about 10 rounds or so. Then it would fail to strip the next round or jam up on the top of the next round smooshing it, or stovepipe. I opened up the gas block about two more clicks and positively cycle again for a few more rounds. Then back to the ejection/feeding issues. Looking into the magazine while clearing things, the rounds on top the magazine were FILTHY from all the crud getting blown back into the system. So maybe 20-30 rounds before it encounters any issues. I can't imagine it's the NiB bolt... these things are really slick. But the chamber is pretty tight to begin with - barely closing on a go-gauge.

Is this issue being caused by too conservative of a gas port setting?
Or is there getting to simply be too much fouling between both the chamber and and incoming rounds?
Should I swap the Slash Heavy Buffer for the original DPMS LR308 CAR buffer?

I assume the action is good and wet with lube.

Just a thought... If it was cycling well without the suppressor and only started balking when you installed the can could it now be a little OVERGASSED? Overgassing could definitely cause a stovepipe as the empty doesn't have time to get out of the way. If I were you I would go through the gas block adjustment process with the can installed.

Don't have any experience with adjustable blocks OR suppressors but the post was about to drop off the front page with no replies... someone here has the answer.

It sounds like it could be overfunctioning.. try dialing it down with the suppressor on.

I used Hornady One Shot that leaves behind that slick dry lube film and the BCG is NiB. So it's a slick thing when it's clean. When I took the rifle apart, the fouling and dry-lube made some sort of caked on clay-like sludge that did not even wipe off easily with my finger. NASTY. I think it might've been better run dry. I'm going to change up lube to something wet and thinner like Rem Oil or Kroil and retune with & without the suppressor. If that doesn't work, I'll try the lighter buffer. I'm thinking the lighter buffer might be easier for the gun to cycle and take less gas to unlock - so less crud in the receiver altogether.


That's what thought fro a moment becaue some of the malks were double feed (next round and unsucessful case ejection), so I took a few shots without the suppressor but it had trouble ejecting & stovepiping... sometimes not stripping the next round off the mag. Definate signs of shortstoking and opening up the gas a little gave me a bit more trouble free shooting.

Use real lube.

Mobile 1 works great and is readily available.

Kroil is not lube.

Why can't you imagine it would be the BCG? NiB is slippery, just what you don't need for an extractor.

Question: when it does eject, where is the brass landing? That will tell you a lot.


-Stooxie

Ok, clay like substance could definitely affect function. Is there a reason you don't want to run CLP, Slip 2000,  or dirt 15w40 Rotella T for that matter? I want the lube I use to stay put and keep the action "wet" so fouling doesn't become clay like. I guess the can might mean you get some spatter on your glasses in the first string of fire... but the rifle functions.

AR10's need lube.  Use Slip2000 EWL or thick motor oil-like lube.

What is your gas port diameter?

How is your gas block attached to the barrel?

With a new adjustable gas system, the gun needs some time to foul in the crevices of the block before you can expect anything consistent from it.  Same with the bolt tail and gas rings.

If your Bolt Carrier doesn't have the critical bore diameters machined right, it's going to be a malf-o-matiic.

I was loving that Hornady One Shot Extreme on pistols because the corrosion protection is amazing and the slick surface never evaporated away. Great for pistols. So I cleaned my rifles and applied it a few months ago to them. The AR15 and WASR tolerated it better... but the 308AR10 not so much, I suppose. I won't know if that was ituntil I try something new. Probably the rem-oil or some Mobil 1. I'm also going to go with different loads.


It would usually bounce off the stall wall. from there wherever it felt like bouncing.
i think the only thing that's telling me is the weather needs to get warmer so I can go outside.



No idea on the diameter. It was mfg as a 14.5" carbine-gas barrel so I'm assuming it's fine.
It was a tight fit to slip and wiggle it on. Gas Block is set-screw style with dimpled barrel - installed by randall at ar15barrels.
Well, the bolt has plenty of fouling in it now!

My third-string plan is to get a new black nitride BCG - and that is also made to allow a tad more headspace for easier extraction...
but it's cheaper to try the lube and buffer swap first.

Overgassed. Close the gas off and work up. Think of it this way: the can will not decrease back-pressure. if it barely locks back unsuppressed, adding the can is going to speed the bolt way up. Odds are you won't be able to have it run both with and without that setup on one gas setting.

 

My OBR with port switch does the same thing with my saker (which has more back pressure than the recommended Surefire) on it. Flip it to suppressed mode and it's only malfunctioning on the second to last round in the mag and only half the time at that now. I'm about to start playing more with springs and buffers.

I had same problem with my rig. It drove me crazy for awhile.  I would turn the gas up and it would run good for a few rounds. Then when I would get on a sounder of hogs one shot then stove pipe.  I started going down on my gas until I got it right. Shot 100 or so rounds through it with no issues.

I am only half-joking when I say this, but after hearing about that mess Id probably drizzle about a tea-spoon of motor oil over the carrier and especially the bolt before trying again!

It's gonna foul...don't worry about it..just shoot it wet..put in a regular buffer and adjust the gas block down to a more restricted opening. I have mine on 5 clicks from closed (SLR block) and works fine on both suppressed and unsuppressed.  Too much Gas makes the bolt fly back too fast and can not pick up the next round correctly and it pops out of battery causing a jam.

Use a standard buffer and spring then adjust the gas setting.

Agreed. Using a heavy buffer and an adjustable gas block is duplication of effort. You use an adjustable gas block to tune down the gas flow so that you don't need a heavy buffer. If you have a non-adjustable gas block then adding mass to the system is the only way to slow it down. A = F/M, you either reduce the force or add mass. Well, you can do both but it costs another $110 .



-Stooxie