To clean the gas cylinder and the piston, you can soak then with a carbon removal chemical like Slip 2000 Carbon Killer, followed by brushing.
Use a soft wire to clear the gas port into the barrel. Ordnance used a specific size drill USED BY HAND to clean the port but be very careful. Damage or enlarge the port and the barrel is ruined.
The piston itself can be wiped clean with a Lead-away type cloth. These cloths wipe leading and carbon off by simple rubbing. (DON'T use on blued guns).
DO NOT use any steel scraper or tool to clean anything. Any scratches will cause the assembly to foul faster and worse.
DO NOT use any abrasive of any sort, including sand cloth, steel wool, Scotchbrite pads, etc.
If you want to scrape, use brass scrapers made from brass rod.
Use a brass brush to scrub the threads in the cylinder and nut.
After thoroughly cleaning, test fit the nut into the cylinder. If it seems to be sticky or damaged in any way, replace both the nut and gas piston. They're cheap and can prevent damaging the barrel.
Keep ALL lubricants, bore solvents, or anything else out of the gas assembly.
It's designed to be used bone dry.
With USGI spec ammo the Carbine gas system is self cleaning and lubricants and solvents will only burn into a sticky tar-like gunk that will cause the pistol to freeze.
Clean the Carine with the sights down on the bench to prevent solvents or lubricants from running into the gas system.
Last, Ordnance staked Carbine gas piston nuts to prevent them from unscrewing. Loctite would work, but will break down from the heat and the nut may unscrew, so staking is still best.
To stake, get a center punch and round the point off so it's not sharp.
Remember, the object is to move a little metal into the gas nut to prevent it unscrewing, NOT to put punch marks in the metal, so round the point well.
