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Weg, how dirty is "dirty"? I have noticed that when shooting my 5.56 upper suppressed, even with the gas-piston system, if I remove the magazine while it still has rounds in it, the metal of the remaining cartridges is dull and obviously dirty with something, although it is more like a dulling of the metallic sheen, rather than visible crud. The magazines appear to get dirty faster too. The dirty cartridges feed just fine. Unsuppressed, the gun runs clean as a whistle with the GP operating system. It just gets a little noticeable dulling of the metal finish on the barrel around the gas block (it's a matte finish stainless barrel), which wipes right off. I'm asking all of this, because I'm curious how much of the dirt in your gun is from the pistol-length gas system, and how much is from the suppressor?

I find a large amount of un-burnt power in the lower, on the magazine, and on the carrier group. I have not done any extensive shooting unsuppressed so I can't comment on the whether it is different without a suppressor. I'm pretty sure the un-burnt powder is not coming down the gas tube as there never is any on the inside of the bolt carrier when I remove the bolt for cleaning, so I assume it is blowing back out of the chamber from the back pressure caused by the suppressor? I reload with AA1680, and at first I was very worried about the un-burnt powder, but since my velocities are consistent, along with group size, I quit worrying about it, but it's definitely un-burnt powder.This is all with .300 blackout subsonic handloads. With milsurp .556 suppressed I have no unburnt powder, just a lot more powder soot buildup in the receiver, much worse than without the suppressor.

"One thing..... and others can correct me if this is wrong.... but it seems that the only way to get a suppressed .300 Blk SBR to cycle reliably in an AR platform is to (A) avoid gas-piston systems generally and (B) to stick to pistol-length gas systems specifically. That first one breaks my heart as I've become a devotee of gas-piston systems, and the direct impingement SBR upper will just end up pooping all over the innards of my 'til now pristine AR15...... which of course is perfect justification to build out another Spikes Tactical/Timney/MFT lower to keep my 5.56 carbine upper mounted on.

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Mine has a pistol length gas system with a 16" barrel and it functions fine with everything, and yes, it gets very dirty, especially with the suppressor on it.

I have a .300 Blackout AR. I bought it for suppressed shooting, both target and hunting. I started hand loading it and have found it to be reasonably affordable. I have a Gemtech HVT-QM on it. I have shot 3 deer thus far using hand loaded sub-sonic Lehigh Defense 194 grain Maximum expansion bullets with no issues. Overall, if I was not wanting to shoot suppressed and as quite as possible I probably would have just stuck with a 5.56 AR, but for what I use it for it is great. I have never had jamming or feeding issues with it, and my subsonic hand loads work fine.