I shot some corrosive ammo through my M1 and it rusted up very quick. It took me a week or so after the first shooting to get it cleaned(yah, my fault....life's busy).
I look at that and think 'great price' then I think about trying to get all of the crap cleaned out of my SKS and think 'wow...I think i'll wait'!!
Yeah, if you wait a week to clean the gun it'll rust with corrosive ammo. Clean it the day you shoot and it's fine.