this isnt the best way but it made mine look ok.
I started out be drawing the template on on piece of cardboard. then i transfered the same thing on to another.
Next i got a meter stick and cut out on another piece of cardboard long equal width strips. Then i cut them out according the the turns of the rifle.
After i hot glued it all together i went back and added in the other detail using small flat pieces of cardboard.
I am not making anything out of cardboard so I assume the process mentioned by .DOom. is correct. If you want to add onto it or smooth out the surface so you have a really clean finish you could probably resin/fiberglass it when you get the general shape (has anyone done this? I'm not 100% sure it would work). If you can't do that, you could possibly use duct tape to make the edges a little less harsh.
On another note, double and triple posting (as it appears you have done) is looked down upon and if you continue double and triple posting topics, you may be met with a ban. Try and keep slightly broader topics and utilize one topic for more of your needs. You probably could have put all of these questions in your first topic with a slight change of title. Good luck with your weapon making.