I just bought a 552 yesterday that was like new. (a 73 vintage rifle). I cleaned it good, as it had been fired, not alot i think, but never eaned. I shot about 350 shots through it today, slow, fast, fast as I could for 15 rounds, and not one jam.
.22 auto's are blow back actions so bits of unburnt powder get dumped inside the action on most designs. mine had that green/gray color from the coatings they put on the powder. alot of times you can feel the grit when you manualy cycle the action slowly.
clean them when they get more that just slightly gritty and you won't have a problem, always use proper fitting hollow ground screwdrivers and none marring tools.. keep in mind that the reciever is a casting. and scratches easily., you don't need a hammer or cheater bar to realy tork the screw thot hold the whole thing together. put at bit of moly in the reciever so the barrel, bolt and operating rod slide in snugly but without force.
don't clean too often, because it will get dirty the first time you use it any way, i pull a patch of hoppes #9 through the barrel and then some dry patches. I wipe the gun down and and don't worry about complete tear down untill I think i feels gritty enough. Just something you figure out for your self how much grit you can take.
