You could edit your post for clarity. Sometimes you appear to say "Powerline" when you seem to mean "Powermaster". The Crosman pistol looks readily restorable. Order a barrel from the factory. It should be cheap enough. Find a nice piece of wood (or anything flat and thick enough, really), and make ...

How about something like a PEST, but with a pneumatically driven rotor?

Or better yet, use an air tool to spin the rotor. Maybe a Harbor Freight die grinder or something.

I'd say that could complicate feeding... It would be kind of hard to feed that mag into something homemade unless you have machining capabilities. I see what you mean though. I don't know about that. I bet you could mold some epoxy putty or Bondo or something into a suitable magazine well. A projec...

A project I've been thinking about is to get something like this or one of those cheap mini-AEG's, and to configure the piston as a striker to hit a CO2 hammer valve. Since the action would be electrically actuated, you could even salvage a valve from a pump action paintball gun. Or, some gas powere...

Leather dye is often used to stain other things. That would certainly be worth some experimentation.

Do you think spray on truck bed liner would be worth a try?

Do clear coats do anything significant for scratch resistance?

The Frankford Arsenal silencer book assumes the volume of a typical firearm suppressor being 20 times that of the barrel in a calculation chapter. A significant part of silencing is slowing down the release of gas, accomplished in one way through simple expansion. I'm curious what could be achieved ...

Yeah, definitely ditch the tape and hide the wires. The straps on the stock are ugly. The pistol grip doesn't seem level, but I don't know how much you can do with that. Is it mounted far enough forward so you can rock in magazines properly? Sights would be good. Is the rear sight located far enough...

You might be interested in the classic airsoft "bullet valve".

http://classicairsoft.org/images/BV.htm

http://s34.photobucket.com/albums/d124/smims/?start=20

http://www.google.com/patents/about?id=rFY5AAAAEBAJ&dq

Wow, I am extremely impressed.

With the exception of the one brass gatling gun linked to on the first page, every other gatling potato gun I've seen is little more than a pile of ordinary potato cannons duct-taped together.

This, though, this is something unique. Nice work .

I'd like to see if I can build something along the lines of a classic airsoft style BV unit, although a $0 budget and no transportation is a serious problem for the meantime.

I'd also like to experiment with lost foam zinc casting.

It would be an interesting experiment to see how far you can shorten the t shirt material until stability is lost.

I was a member on Spudtech.

It's been explored to some degree, or at least with nerf darts.
http://www.boltsniper.com/Homemades/BSarmory.htm

Feeding a ball doesn't seem that problematic. I think a lot of the attraction to pepperbox designs is more so for propellant issues than feeding issues.

It's not really the rifling on a projectile that stabilizes it. It's just left over from the rifling imparting a spin on it. With rifled shotgun slugs, the rifling allows the projectile to safely swage down if fired through a choke. Look here: http://www.spudfiles.com/forums/air-rifling-t16401.html ...