Okay, here's a quick update.

I emailed CMMG and got great feedback, they were prompt and helpful.

I sent these pics to the them and they said that the little sand like particles are unburned powder. I had thought the same thing until I read about the filler that is supposedly used in some subsonic ammo.

They also recommended turning the gas screw out a couple clicks. The tech said that when running subsonic ammo even with the can there just isn't enough pressure to begin with to properly cycle the action. This is were I get confused, it would run better without the can than with and you would think there would be more back pressure with the can.

I just emailed them back and asked about that as i was busy working earlier and didn't think about it.

This is after one shot.

Maybe this isn't even dirty but I thought so.

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