SpudFiles

When using GGDT how do you find out the dead volume? or what is the dead volume (is it from the chamer, barrel, valve?)?

Dead volume is the space between the valve and the projectile

ok

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?

and how do you solve this: WRN: barrel possibly restircting flow... (or something to that effect).

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 diameter. Clear as mud now?

Yes it is much clearer then mud... i thought when it said chamber outer and inner diameter it meant the ID of the PVC and the OD of the PVC used for the chamber!!.

how do i fix this:

im not that good with GGDT but i think that means the barrels to small? i get that all the time and i dont know why do i just said forget it and started using my own method for finding the fps of my guns (only reason i wanted to use ggdt was to find fps.)

well, im using a 2" chamber with (hopefully) 3/4" barrel (if i can find it).

22" chamber 37" barrel

yeah i do belive that barrel is way to small for the chamber size try using a 1/2" barrel and see how it does 1/2" barrels are perfect for AA's you might need some wadding for them.

Ehh i use a 50mm chamber(2inch)with a 20mm barrel it says the barrel is restricting flow but its still capapble of 800fps so im happy as pie.

Yep, I just checked the GGDT by playing around with my gun design and when I shrunk the barrel it said "barrel choking flow." The gun will still work good but it just won't let out all the air. I guess what the program is saying is, "Save your money, use smaller chamber!"

No, it's saying that your barrel is too small to use all the air that the valve is providing it with. "save your money, use a smaller valve", if you will.

With co-axials, this'll crop up in two situations:
1) You've installed a barrel insert, and thus are using a 2" valve with a .68" barrel. Yeah, just a tad of flow restriction there.
2) You've used the "CV flow values" option, and entered something like "50" for the flow value of what is really a .68" valve. Same situation as above, just a different way of telling you that your 2" valve is not the flow restriction.

yea it only says it if i bring the psi to like 300+ other wise it says no errors