Slip2000, BreakFree, Hoppes #9
Cleaning the SLP's gas piston is very difficult, but the best solution I've found is to first start by soaking it in the SLIP2000 gas piston and choke tube cleaner for about 10-15 minutes, then rinsing it under cold water while gently scrubbing the little holes with a soft old tooth brush.
Then I thoroughly dry it with a soft towel and blow dry it on high heat for about 5 minutes until the piston is completely dry and VERY hot.
When hot, I take it outside and spray Break Free CLP inside, outside, and into all the little holes, then i spray some Break Free on my toothbrush and gently scrub inside each hole, inside the piston, and at the edges. Scrub for about 2 minutes, then pat dry.
Finally, I wipe it out with a fresh soft towel and it's ready to go directly back into the firearm. Note, if you go this route, you do not need any extra lubricant. I've found that its best to just use a very light film of lube on the piston, if you put excessive lube on there, it just provides more surface area for fouling to stick to.
The SLIP2000 does virtually nothing except loosen up the fouling, the piston doesn't come out looking as clean as in the pictures above. Break Free is the only thing I've found that works on it.
It may interest you to know that when I fire cheap shells like Federal Multi Loads (never putting that in my gun again), it tends to gum up the gas system much more than when I fire quality ammo like Winchester AA.