The gas system on your M14/M1A should be cleaned after roughly every 500 rounds or if you begin to experience cycling issues. If your rifle does not pass the tilt test, it may be time for a cleaning as well.
First, begin by making a witness mark on your gas plug and gas lock so that you can apply the same torque upon installation. If you have a torque wrench and set by torque, don't bother with the witness mark. You can also use a sharpie or white out.
Secure the gas cylinder with a gas cylinder wrench or a crescent wrench with a rag or tape around the jaws. Using a BAD-T1 tool, USGI multi-tool or a 3/8" boxed end wrench, loosen and remove the gas plug.
If you have the BAD-T4 gas cylinder wrench, ensure the threads are clean on your gas plug and screw it into the BAD-T4 wrench as pictured. This will give the plug a nice handle when cleaning and will also prevent it from rolling around on the bench.
Using a nylon brush and some powder solvent, clean the exterior of the gas piston and completely dry when done. I also used a bronze brush gently on the stubborn carbon build up areas and the carbon came right off without much fuss.
Once the exterior of the gas piston has been cleaned, insert it into the "D" cut of the BAD-T4, BAD-T1, Sadlak gas cylinder wrench or Smith Enterprise gas cylinder wrench. This creates a handle for the next step. Obviously, if you have neither, then don't worry, you can get by without it.
Next, clean the inside of the gas piston with a letter P and number 15 drill bits. You use the drill bits to scrape carbon from the inside walls of the piston. Lots of black dust will come out. This is normal.
Note: when performing all scraping, be careful not to remove metal from the gas system components! To avoid cutting into the metal, you can grind about 2/3rds of the cutting tips off your drill bits to prevent damage to your gas plug and piston. I then smoothe the grinding with an Arkansas stone.
Now use the letter "O" drill bit on the gas plug and do the same...
Use a bronze brush with powder solvent to clean the inside of the gas piston and dry thoroughly with q-tips or cleaning patches. The inside should be clean and dry
Do the same with the gas cylinder and dry thoroughly. Insert the gas piston. lock the bolt to the rear and make sure the gas piston sinks down all the way...(this means the gas piston tail is lined up with the "D" cut in your gas cylinder) (Note: all gas system components should be completly dry and free of oils and solvents upon re-assembly. Oil can be used in a pinch to get a seized gas system to work but it should be disassembled and re-cleaned during your next maintenance session)
Ensure the threads of the gas plug are thoroughly cleaned and dry. Apply some anti-sieze to the threads.
Using your gas cylinder wrench and tool of choice, torque the gas plug to match the witness mark you made before you disassembled the gas system. If you are using a torque wrench, the minimum recommended torque is 120 inch pounds (10 foot pounds) and the maximum is approximately 23 foot pounds. The popular ranges are 120 inch pounds to 150 inch pounds. Gas plug torque may affect accuracy so play around with what torque works best in your rifle. German torque is also acceptable (Good-N-Tight)
The gas components pictured have just under 700 rounds through them and they cleaned up very nicely. It was a USGI gas system with a Sadlak TiN gas piston (no groove). YMMV
7Thanks
Cleaning the gas system 
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