Went to the range on my lunch hour today.  While I was shooting a rapid fire string of ten rounds, after firing 30 rounds slow fire, I noticed smoke coming out of the holes in the handguard.  I initially thought it was oil baking on the barrel.  But, upon further inspection the first three inches of the gas tube coming out of the front sight have what looks to be powder fouling.  Is this normal?

I realize the smoke may still be from oil, but am mildly concerned about the leakage.  I don't want my fingers to get stung someday when I'm not watching where I put my hand.

Kent

While I've noticed small amounts of fouling around the gas tube on my ARs, yours sounds a bit excessive to me. Haven't lost your gas tube retaining pin have ya? Tube nice and tight? or Improperly aligned?

Mike

If rifle functions fine, do not worry about it. Fairly normal, kind of hard to seal 50,000+/- PSI with a "slip fit" joint. Carbon will build up and lock clog the clearance, then make for PIA if you decide to try to remove tube from sight base.

I also have that, When I inspected all was ok so I guess it is normal. Like mr_wilson says make sure the pin is in and tube is not moving around. Also I put some lithium grease the white stuff around the front sight where the tube goes in. I shot it without the upper hand guard in place. I watched to see if the grease blew out from around it. It didn't so I figure it was tight in there.

Thanks for the responses.  It is a fairly new upper, around 200 rounds now.  No functioning problems.  I'll check the things Mr. Wilson mentioned, and if all is OK I'll stop worrying.

Thanks,
Kent

Well, what we do down here in Alabama, when out working on AR's under the shade tree(and drinking iced tea, JD or whatever)..knock the pin out, remove the gas tube, clean everything.  Then spray the first 2inches of the gas tube(the end that goes back into the sight assembly) with Brownell's teflon moly or similar paint.  when assembled, this will tighten the joint and seal it..sometimes you just gotta improvise. MD