SpudFiles

For the choke you could cut the barrel with a pipe cutter this usually leaves a small bur on the inside which will act as a choke.

A burr would NOT work as a choke because a choke gradually constricts the shot.
The longer barrel would definitely help, as would porting and crowning the barrel (crowning is like cutting a reverse potato knife on the inside of the barrel). porting and crowning negate turbulence on projectile(s) as they exit the muzzle since it creates a transitional area instead of going from high pressure to ambient pressure instantly. By removing some turbulence, the shot will hold together better.
you could make a choke tube by getting 3-4 inches of very thin walled steel tubing that fits tight in your barrel, file the inside edge where the shot enters to make it smooth. attach this in the muzzle and you will have a choke tube

a friend of mine puts gasoline in a spray bottle to mist it into the chamber,
he swears by it, I like pneumatic myself

Really kool job. It looks sweet! In stead of wood try and get some Diamond plate. That would look even kooler.

Ya, the wood looks crappy and I will make it out of aluminium. It should be done in October because all my money this month is to get a paintball marker/set up. If I don't start paintball this month I will most likely die.

oooo idamond plate would be awsome but how much it cost?and thenn you have to cut it.