the new "expert grade" CMPicon rifles have refinished receivers, new barrel and wood, and at least on the two I have, they refinished the gas cylinder by painting with something. It has a glazed on, spray-ain't look. But I imagine their surface prep isn't very time consuming. Give them a call and ask what they used. My guess would be flat black epoxy paint like Brownell's alumahyde (did I spell that right?). I would never use it for this purpose, but it did wonders on the receiver of an old Glenfield 70 I restored for the kiddos. Hasn't chipped, tolerates any of the usual cleaning solvents. It would probably look better on a glass cylinder if there were better surface prep.