So... I'm going to build a launcher.

Hey all,

I've been looking for some more projects to keep me busy. The first is going to be a pump-pneuMag for which I'm sourcing parts now. However, having played mostly scenario lately, the merits of anti-artillery firepower are becoming clear. I know that there are some pre-fab, very nice options out there. However, they are generally VERY expensive (considering the limited utility) and tend toward the cumbersome.

So... I'm really just at the drawing board so far. There are a few things that I definitely want included:◦Relatively small (akin to the Metadyne launcher, perhaps the m79 Thumper [see "stock"])
◦Regulated air: Going to use a reg. Period. I'd like the flexibility of using 12g CO2, CA CO2, and HPA. The only way to do this is to build with CO2 in mind and regulate pressure to the dump chamber so that shot pressure is consistent regardless of input.
◦CO2 compatible: obvious, but important to keep in mind when choosing components.
◦Portability: I don't expect to carry this as a primary, and I don't want it to be so cumbersome that it sits in my gearbag as a show piece.
◦Stock: I definitely want a stock, but with weight/size concerns, a traditional wooden stock is impractical. I know there are paintball-specific options available and may go with one for cost concerns. However, I really like the top-folding stock on the SPAS-12 (See Robert Muldoon in Jurassic Park), which is unfortunately not made anymore and costs around $1000 if you can find one. Similar top-folding shotgun stocks are available for around $60, still more than I want to spend for that component. WWII Paratrooper folding wire stocks are also interesting.

Question marks: These are the things I'm still working out and really would like some input on.
◦Actuation: Mechanical actuation (trigger) is the simpler in terms of operation, but electronic actuation opens a lot more doors of possibility, not the least of which is that the trigger/frame components do not have to be located in any exact physical proximity to the valve assembly/firing mechanism. Which brings us to...
◦Firing mechanism: There are 2 basic options here. Hack up and Frankenstein an existing gun/platform, or fabricate an entirely new platform. Existing platform options are basically stacked-tube blowback, Automag, and spool valve. I really don't know a thing about spoolies, so that's unlikely.
◦Materials: The barrel, in particular, is the first materials question. I believe the Nerf rockets are 2"OD, so I need a tube that's 2"ID. I'd like to go metal. Aluminum is probably best for weight/durability balance, but I don't know where I'd source 2" aluminum pipe and what that'll cost me.
◦Dump chamber/valve operation: This largely falls under the "firing mechanism" discussion. If I'm fabricating, I'll need to figure out the logistics and dimensions of the dump chamber and valve setup.
That's all I've got at the moment. For the record, I'll be trying to scavenge as many parts as I can from PBN and other classifieds and ebay. Building something awesome from stuff other people don't want is part of the thrill. Thanks in advance for all of your help.

John