
#25 on the illustration is the cocking lug. It is what you need to screw out so it catches on the cocking lip of the hammer. To remove the bolt you need to remove grip handle #46 and mainspring plug #27, pump rod #31 from the bolt then pull the bolt back enough that the cocking lug lines up with one of the holes on the right side of the valve tube. Once you do this rotate the bolt so that the bottom of cocking lug is sticking out. Once you do this just unscrew it enough that it catches the hammer.