M26 to paintball

[*F~E~A~R*]

http://en.wikipedia.org/wiki/M26_Mod...Shotgun_System

here is the marker of which i am trying to build i have a clip planned out for it but i need the internal units plan i want it to be semi automatic and any sugjestions would be great.

also how many paintballs per 12 gram do you think it would take?