SpudFiles

I'm building another spud gun, but this time I'm going to put a 5lb spring check after the reducer so I can use fuel ( propane and oxygen) under pressure aprox 4lb. Anthing I should concider in doing this? Has anyone tried this before?

well, It could work, but I am not sure how thick the diaphragm in the check valve is. If it is too thin, than It could possibly melt, or deform. If you really want to put the contents under pressure, I recommend burst discs. of course, at that point, this has basicly become a hybrid, which should only be attempted by very experienced
spudders with steel or sch 80 pvc. I am not really sure. It's up to you.

the gasket is attached to a 1/4" thick puck and slides up and down on a stainless shaft ( spring loaded of course). The entier unit will be sch 80, except the spring check, it is bass. Not sure how to figure out how much pressure will be built in this unit. Or how fast the projectile will be moving.
I'm thinking that my chamber will be smaller than a normal combustion chamber. Any one know that equation for this?

Yes I tried that for a full auto. It could work for a combustion but they have small orfice when open so it will decreace performance.

I can get a ful port spring check that would take care of the orfice problem. Still cant figure out the math end of things. Its been a few years scince I've been in school.