MFS works great in mine, fairly clean but the red stuff around the primers turns my white grease to pink.
I won't talk about accuracy, turns out my scope was slowly going south.
The Norinco copper washed steel case (Can Am) wasn't cycling too well in either of mine, short strokes. Seems to have a lot of carbon residue as well.
Someone suggested the stock spring might help so I put that back in my long barrel and still no go.
When I put the USGI spring and Sadlak guide in the shorty it seems to be cycling fine, I've only run about 30 rounds through it so far but I'm optimistic(fingers crossed).
Might all be my fault though, don't have the tools to properly clean the gas system yet. All I did was solvent soak and pick at it as best I could. A CRT-14 Carbon Removal Tool is in the mail from One Shot Tactical.