I find that when you need thin rubber that bike tubes work really well. I especially enjoy blowing them up by overfilling. Wahahahaha!!!!

Didn't I see this posted earlier? Owell, never mind. Looks better than your last gun, so I don't have a clue why it doesn't work as well as your last gun. maybe you need to play around with your ignition? Have fun experimenting

I like your hybrid man. I've been trying to find a good propane meter design, but I've failed miserably, could you refer me to one?

First of all, I seriously doubt that you could fire a paintball through a metal door. Second, YOU PLAN TO FIRE THIS AT PEOPLE!!!! What is wrong with you! If it goes through metal, what would it do to something soft and fleshy!!!!

if i was making a coaxial cannon, for the GGDT how would i subtract the volume of the barrel inside the chamber from the chamber volume? All you do is type in the outer diameter of the barrel as your chamber's inner diameter. Then you type in the inner diameter of your chamber pipe as the outer dia...

You're right, it's mostly going to be piston.

The GGDT was giveing varying velocities depending on the projectile. Anywhere from 750 to 350 fps. The farthest it was simulating was about half a mile.

I haven't glued on the chambers or the barrel yet and I'm planning on making a stand for the gun. I used the GGDT and it said the barrel should be plenty fine how long it is(hopefully).

Here's my first gun in progress. I researched for a while and finally decided on two things. First, I decided to make a chamber sealing piston, and second, I decided to go big. It has 2 4'x4" chambers and a 12'x2" barrel. I'm welcome to any sugestions since most of it is still slip fitted while I'm ...

the only combustion gun which i'm not really aloud to mkae i said was a simple cannon and left it at that without explainin anything to my parents.

seriously, where did you learn your grammer.

just to correct you, the acceleration due to gravity is 10 m/s or 32 ft/s.
so after just 1 second of his jump he'll already have traveled 16 ft. After 2 seconds he'll have gone 48 ft. So just as a fyi your parachute is going to need to deploy DAND fast, otherwise, splat