Well I can answer some of your questions. Well the back part of it was originally made so a threaded ball valve could be placed on the back. Long story short it didn't work that well. I already had threads there I had to use so I just made it interchangeable with other things. Also under the ...

With talk of burst disks and stuff is Mapp only used with hybrid or can it replace propane in a normal combustion?

Wow man what an awesome potato gun !!!
You are so not a first time gunner from what I've seen here haha.
But yeah really nice gun, you should get some action of it on film.

No I really am I first time gunner. I just did a a lot of research and calculations before I did it. =)

I have to make it a ...

This is my first time constructing a potato cannon. Originally I was having a lot of trouble getting the right fuel mixture, but after adding a fan I'm having 100% success. The measurements of the cannon are 24in of 4in pipe for the combustion chamber and 48in of 2in pipe for the barrel. I inject ...

I figured it out tonight! =)

So I found out first that the propane adapter I got only works when exiting to a lower pressure, i.e. it only works if the meter isn't used. I will fix that in the future with a new piece. I also added a fan the back of the unit. The both of those combined got my cannon ...

Its a grill adapter, so I think that's the problem. I already ordered a tank adapter so it should be ready by next week.

Thanks for your help.

So I have a 8in meter pipe in there now should I change it to 7in or 6in? I guess I have to much in there to achieve combustion. I think propane is not able to combust after about a 9.7% mixture.

Edit: After looking at my calculations again it seems like I could even go for a 5in pipe.

I just built my first spudgun today with mixed results. My measurements are as follows.

Combustion chamber - 4in PVC 24in long
Projectile barrel - 2in PVC 48in long

According to my calculations this should get my to around a 1.75:1 ratio of combustion chamber to launch barrel. My problem is that I ...