First off. It's really hard to say exactly what is going on without one in front of me. From what information has been given, the way I understand it, I would guess you have the piston adjusted too long. That would make closing the last bit of stroke tight as the bumper is getting compressed. Compressing the bumper too much could also be the reason it's hard to open the pump arm and it would be expanded in the tube. As far as valve and hammer springs... I think I would begin by lightening both of them. Just my thoughts. I must say... the gun certainly draws my attention.
Silly question...Is it a 4 pump max gun by design?Did it come with a Manual?
that's awesome ! A huge part of the reason we don't see underlevers on high end guns like the indy is the inherent limitation in lever arm.