Can someone give me a link to a how-to-assemble for the coaxial piston type? I couldn't find one in the search.

OK, could some one give me a parts list and approximate price for the above design?

That launcher looks fine. I said "somewhat realistic" not one of those with like a 6" pressure chamber and a 2" barrel. However, I would like to model my launcher after the rap4 launcher http://www.rap4.com/paintball/os/bazooka-grenade-launchers-p-4990.html , where the co2 bottle screws into the ...

I am fairly new to all of this, when you post an idea, can you show me a picture/diagram as well? Because I don't really get what you are saying in words, at least until I get all of the terms down.

Thanks for the info, but is it possible to do without the piston concept?

I want to build a RPG that uses a paintball co2 tank for power. I will be using nerf vortexes as my ammunition. Also, I would like to know how to make it semi-auto, so I can just drop in a rocket, fire, and repeat (not have to worry about opening or closing extra valves). In addition, I would like ...