Originally Posted by Fubarius
I ran into that issue when I was trying to make the thing work with some really tiny paint. Had the main spring shimmed so much the piercing pin was jamming into the CA adapter and getting stuck. I ended up drilling the tip of the CA adapter a bit more open so the pierce pin can't bottom out.
I really recommend just removing everything past the cupseal, leaving just enough for the valve spring to seat on. In CA guns, the max valve travel is something like double what you can achieve with the 12 gram pierce pin in there. It's very very counterproductive to leave it in a KP3. It isn't even the pin itself that is the problem - it's the spring guide shoulder that guides the pin. It hits the back of the chamber plug.