SpudFiles

I loaded a whole bunch (100's) into the barrel of one of my bigger cannons and ambushed my brother. It was pretty awesome.

I also built a cannon similar to the one youve built, and was able to get marshmallows to go through a couple layers of cardboard, but thats about as much damage as i could get.

I bet you could cause a little bit more damage if you were to freeze the marshmallows first

Leaving them out for a week does the trick. They're still lightweight, but hard as rocks.

I like it. And after seeing yet another first pneumatic that is better than mine, which I am still too lazy and embarrased to post, I hereby establish the B.T.S.C. award, meaning "Better Than Salt's Cannon".

Methinks you won't really need the scope for marshmallows, but maybe if you used darts or ice...

Thanks for the compliment, a lot of time went into making this gun, and I'm glad everyone seems to like it.

Add another guy to the "i like your gun list" please! haha, but i really do! How much did it cost in the end? Oh yes, and how badly do marshmellows sting if youre hit by one??
How long DID it take you then?

The barrel/ bolt action took me a day to make because I found this website days later, so I had to come up with my own way of doing it. I got it working pneumatically with a much smaller chamber, but when I realized the pipe was DWV I scrapped it. It took about a week to get to what you see here.

I didn't keep track of the cost too well, the scope was about 8$, the sprinkler valve was 12$ and I had to buy a few fittings, O rings, hose clamps, and the pipe I used as a chamber. I guess it cost somewhere in the neighborhood of $30 US to make.

I've never shot this gun at a person. I fired some 1/2" marbles. I shot one at my driveway. I saw nothing, I only heard the crack of the impact, and saw the leaves on the top of my neighbors tree fall as though they had been hit by the ricochet.

Haha, I wouldnt shoot anyone with it either then! Thats pretty fast to build a gun, mine is taking ages! So well done! Thats not too bad for the price at all. I have lots of building sites near my house (I live in Cape Town , South Africa) where I can find PVC cut-offs which makes my expenses quite low, and I create my own valves with watever I can find etc etc!
I think Im going to start building a copper marble gun! They sound fun!

Marbles are fun, you can launch them at very high speeds.

Haha, i like thesound of that. And you can make quite simple, yet effective guns just to have fun with and release your anger with! I always have an old reliable gun at hand when Im building a new gun! Anger sucks!

Here is a little update to this cannon.

I replaced the old bike tire valve with a threaded schrader.
I got the schrader from Ace Hardware for $2.80. I was glad to find one cheaper than buying from BCArms.com where there is a shipping cost.

Thats cool, but can I ask what is better about the schrader than just a bike one?? I really cant figure!

The threaded schrader looks much cleaner and sticks out farther in my case. Epoxy'd bike valves tend to leak. Threaded fittings will not leak provided that you use Teflon tape or some other threaded fitting seal.

OK cool, I dont use the normal bike tires either though. I use roadbike ones as I said before which are threaded.
I'll send in a photo of mine tomorrow to show you.

Materials:
1/2" x 1/2" x 1/2" T
1" x 1" x 1/2" T (instead of 1" you can use whatever your barrel size is.
small length of 1/2" sch 40 PVC pipe.
2 small hose clamps

Steps:
1. Bore out the stops that join the two parallel sockets on both of the T joints
2. Trim down both of the T joints so that when you connect them, the scope will be however far from the barrel you want it to be.
3. Cut a straight line through the bottom edge of the 1"x 1"x 1/2" T
4. Cut the 1/2" T along its long edge (cut lengthwise) so that you cut off more than half of it.
5. File the 1/2" T smooth so that you can hold a 1/2" pipe flush against where you removed the stop.
6. Cut a small enough piece of pipe to couple the top and bottom T and cement them together.
7. Split the rest of the pipe, or however much you need in half lengthwise.
8. Cement one half of the split piece of pipe to the top T
9. Slide the scope mount over your barrel, when you get it where you want it, clamp it down.

The point of not just cementing the lower T into place is that you can completely remove the scope if you want, or you can change its position on the barrel easily. This also ensures that the scope mount will not interfere with the projectile (or as in my case the bolt action itself) as it travels down the barrel.

the method u have just shown us i think is excellant ill be making one but i dont under stand why you need a airchamber so big iv seen so many other forums and there small but looks great other wise, please put a vid it look interesting and i would love to see the damage that thing could do