It is said to be a pretty common fixn as some folks have implied that the AS version is the same as the real steel.
http://hk.ghqst.com/pdf/USPDD.pdf
This is a real steel teardown, I've read through it and compared to my KSC and from the grainy photos it sure looks close. I have not attempted to follow these instructions and tear down my.
Quoting from another website on this
"The above guide is spot on upto the point of taking out the main sear, in the airsoft version this a main sear and flow valve hammer assembly and can not be removed until the metal frame has been lifted out of the plastic, at this point you need to put some pressure on the assembly pushing it forward, the take down lever can then be pulled out(i'v found with the lever pointing down is easyer) and then the hammer axis pin from the other side, if it sticks just put a bit more presure on the sear assembly.
hope this helps "