if you know that little about how pneamuatics work then stick you compressed air. If you screw up with C02 you're going to kill yourself. Air compressors supply plenty of pressure for most people and cost about the same as a palmer. A safe solution you could use is this:
http://www.lowes.com/lowes ...

the 120 psi thing is probably a plus because it'll keep stupid people from overcharging their cannons. If you want higher than 120 palmers still work great, but I think this is a simpler solution for people new to C02.

Hey I saw this the other day when I went to Lowe's and it's the most perfect thing I've ever seen for c02 regulation. it costs about the same as a palmer, looks a lot cleaner, and needs no additional fitting to hook up to a regular 1/4" npt quick connect. What do you think?

http://www.lowes.com ...

the chamber is sch80 just because I happenned to have some left over from something else. I'll put those screws in though. I won't be firing over 70 psi so I'm not worried about the barrell blowing up one me.

This is my second pneaumatic cannon. It uses a Cobbs valve (1.5 inch porting piston valve in a 2 inch tee.) It has 4" diameter 27" sch80 chamber and a 3" diameter 30" barrel. My first test fire I shot a t-shirt from my garage out of the end of my culdesack at 40 psi and nailed my neighbor's house. I ...

it shouldn't cost more than $1 to get a new screw, just take one of the other ones to home depot and have them find one like it. I think you might have to cut the end off the screw, but that's not that difficult. It probably wouldn't give you any problems, but it's an easy fix.

edit:before I tell ...

I give up, I found 29 and some other fun things, but I can't find that elusive #30. here's what I have

1 http://www.spudfiles.com/forums/viewtopic.php?t=3304& <--Kevin
2 http://www.spudfiles.com/forums/viewtopic.php?t=4135& <--Mauler (you needed a cannon to test fire)
3 http://www.spudfiles.com ...

Thank you, Thank you. *Takes a bow*

I'm working on sgort's too, but I've only got 25 so far.

http://www.spudfiles.com/forums/viewtopic.php?t=2974&
http://www.spudfiles.com/forums/viewtopic.php?t=4549&
http://www.spudfiles.com/forums/viewtopic.php?t=3573&
http://www.spudfiles.com/forums/viewtopic.php?t=4919&
http://www.spudfiles.com/forums/viewtopic.php?t=4918&
http://www.spudfiles.com ...

what gun are you using that fires at 200 psi?

the PVC ballistics breech loader is for a 1" barrel, I've looked at it before. I'll have to give that other suggestion a try though. That's 4" sch40 right?

yes it's over under, with a 27" long 4" reservoir. The barrell is 30" long 3".

I've been looking around for awhile now and I need some help deciding on a design for a breech loader for my cannon. I use it to shoot t-shirts out of a 3" barrel. I've seen alot of good designs that I could do for smaller barrels but there aren't very many of this size. I built the cannon with way ...

I'm planning on using a spring from a weed wacker as the spring to seal my chamber-sealing valve. Is this going to be too strong? or what is a better alternative (they're pretty much the only kind of spring I could think of.)

I was looking at routing the pipe over the shoulder though, not using hose, and having the ball valve seperating the two tanks. My two main concerns are that the recoil might stress the pipe or that the ball valve idea won't work.