Hi all,
I was just rearranging the handguard covers on my BCM upper when I happened to notice a rust-colored residue of some sort on the top of the barrel and in/around the cuts in the handguard. This residue only appears on the top of the barrel to the rear of the low-profile gas block and under the gas tube. It does not appear in front of the gas block nor the rear end of the barrel or handguard closer to the receiver. When I rub some off with a Q-tip it appears blackish, but on the barrel and handguard it appears more rusty color. I'm just wondering if there's anything to be concerned about regarding gas escaping improperly, etc. The rifle shoots fine. I wouldn't have noticed anything had I not removed the rail covers. Maybe it's just residue from the gas tube getting hot while shooting, and all is well. That's likely it, but just wanted to check. I can upload pics if you like, but I think I described the situation pretty well. Thanks for any insights you may have.
P.S. I just cleaned the residue off the barrel and rail with some rubbing alcohol and Q-tips. Going shooting tomorrow and I'll check if there is any additional build-up.
Chris
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