AT Weapon Concept: Breach-Loaded Air Cannon

Ok. So, recently I considered going to OpGen, but on the stipulation that I could bring an AT weapon. Only problem was, I didn't have an AT weapon (I have since considered just going to OpGen as a soldier, though). This got me to thinking, as I have the old solenoid valve from my prototype air cannon (which was never tested) at my apartment. I started digging through youtube and my old paintball armor resources and have thought about something for scenarios and general play: a bolt-action, breach-loaded pneumatic air cannon.

*The following is theory and concept design, not (yet) physical construction. All piping listed conforms to ASTM Standards*

Design:
The design, due to limited resources, is Schedule 40 PVC-based. It consists of a 1' long, 3" diamater PVC pressure chamber with a simple fill valve, emergency bleed valve and pressure gauge. It is reduced down via couplings to a 1" solenoid operated sprinkler valve rated for 110 PSI. It is then widened back up to 6" of 2" diameter PVC barrel. There is also a separate piece of 2" diameter PVC that is about 3-4' long, equipped with a muzzle brake. These will fit inside a larger piece of PVC, the mechanism which will allow it to be a bolt-action cannon. The long piece will have a handle allowing bolt movement.

The solenoid is wired to a firing box that contains 2 internal 9v batteries plus one externally-mounted battery (which can be disconnected to act as an electrical safety), plus a main power switch and indicator lights. The box is also connected to a trigger switch mounted elsewhere on the gun assembly.

As for the compressor systems, those are still being worked out.

Firing:
The cannon opens by sliding foward, opening the breach. The round (a 2" diameter SOFT Nerf rocket) is loaded into the foward barrel and closed back. The two pieces are designed in such a way so that when closed the forward barrel rests against the 6" piece. The air chamber is pressurized to around 70-80 PSI (though not exceeding 100 PSI for safety precautions). The safety battery is connected and solenoid power is flipped on. After confirming all is secure, it's just a simple pull of the trigger switch.


*End theory*

Before I even think about going to work on this, I want the thoughts of some of our much more engineering-experienced members.

I think ive made something like this before, except I used hair spray as the propellent and broom handle to shove the projectile (potato) into the breach, i then used long grill lighter as the ignition source.

It sounds like a solid concept, the only problem I see is that from the description it seems like its going to be kinda heavy, and its going to have a structural weak point at the choke point.

This is true. But to be able to use it at some events, combustion won't do =P

This is true. Weight might be an issue. However, I don't intend for it to be a shoulder-mounted cannon. This will be a prototype for a mobile gun emplacement, which will later evolve into a tank's main cannon.....WAY down the road, that is.

Sounds ambitious. How much will it cost?

Considering I already have the $25 sprinkler valve, it's probably only going to take about $30 to complete (just need pipe, a couple fittings, electronics and the fill valve/pressure gauge. Maybe less depending.

http://www.xinventions.com/main/spud/pac6.htm

My cousin made one of these that shoots tennis balls.