Whenever one of my lower Orings on any of my KJ mags goes quagmire on me I just replace the whole damn valve since Ive never been able to find the right sized Oring at any hardwear store lately.
http://www.airsoftparts.ca/store2/in...roducts_id=646
For KSC even though it says glock I wouldsee if these are compatable I would recommend picking some of these up and just replacing the whole valve.
http://www.airsoftparts.ca/store2/in...roducts_id=890