I have found a MK18. How badly does it corrode the flash hider? I saw an AAC brakeout that was corroded badly after 3K rounds. I am not waiting 2 years to get a Larue OBR. I do like the idea of a factory gun, though. Noise will be handled by a can.
I'll see if I can get a pic of mine tomorrow. It's got a couple thousand or so through it.