I got a dog rough one to play with so where Ive had to modify and improvise a bit. I stripped this right down because the stock was cracked and loose.
Undo and remove 2 screws on metal butt plate. Use a socket to undo the nut in the stock (a 9/16 AF fitted the one in mine) and the stock should slide off.Undo the cocking arm pivot screw and remove cocking arm. (on mine the thread was gone in the breech block so I tapped it to 5mm and made up a locknut out of round bar,which I cut a slot in and blued). Undo the locknut on the trigger adjusting screw and remove the screw. Remove the 2 trigger guard screws. You should be able to unhook the trigger spring now but mine was a bugger because of gunge. Unscrew the trigger pivot screw and remove trigger.Unscrew barrel pivot and remove barrel. You can remove small screw on side of breech if you need to get to plunger and its spring. On mine the cylinder end cap was tight so I had to get it into a vice to start to unscrew it from cylinder.Once unscrewed you should be able to remove mainspring and piston. (mine was so gunged the piston washer was stuck to the end of the cylinder. If the piston washer needs removing you will have to drill out the locking pin that holds the piston washer screw (look closely and you should see it).