looking for a bit of help please

[grum7n7]

I have made many potato guns and that have all been combustion with hairspray. Now I want to make a combustion gun using propane. I have read up on all the propane injection stuff and started to plan out my gun. It is supposed to be a sniper.

here are the specs I wanted:

barrel = 40" x .5" \
-------- gives the .8:1 ratio
combustion = 8" x 1' /

so i got those then i got the amount of propane in ml to be mixed in the chamber at 4% and got

amount of propane in chamber = 4.12ml

after this i solved for the meter pipe volume with 90 psi and got...

meter pipe volume = .041 cu. in.

then using the meter pipe volume i calculated the length of the 3/8 meter pipe (actual inside diameter = .46875)...i came up with

meter pipe size = 3/8" x .24"


what am i doing wrong? isnt a length of .24 inches a bit rediculious??? any sugestions of what i can do??? did i make any mistakes???

keep in mind that this is my first gun like this

all help will be appreciated guys


thanks,

nick

[dan116]

you can put a regulator on the propane and reg it to a lower pressure, then you can have the meter at a longer length. If you need good instructions go to burnt latke's website.

[mark.f]

Yeah, the constant pressure system is kind of innacurate and unreliable anyway. A regulated meter, (either by hand or an air regulator), with a longer meter pipe, (but not too long), will provide much more flexibility and service.

[grum7n7]

Aright cool thanks guys. Now that i think about it, that is quite an obvious solution. What pressure would you guys recommend. Or how long of a meter pipe would you recommend and i can get the pressure from there.

Also one more question now. This is possible to have the porpane tank, the meter pipe and the 2 ball valves seperate from the gun right. Like say i had a bike tire valve and a valve on the propane contraption after the second ball valve and insert?

[dan116]

Well, it's all up to you on what pressure you want it and the size of the meter. Also yes you can make an offboard meter, you can find two on advanced spuds and also one on neospuds, they're both offboard but different styles. Hopefully that was helpfull to you.