SpudFiles

hi im new here, well yesterday i made a potato gun, it has a 4in I.D. chamber that is 20in long and the barrel is 2in I.D and is 20in long, is this good

Your barrel could be like three feet long and with that change the gun would have better performance.

I would put a longer barrel on it. It will be extremely loud with a 20" barrel, and with a chamber that size you could extend it up to about 8 feet if you want to get the most power possible.

Consider putting an 80mm computer case fan in the chamber. It will increase preformace.

well i want to shorten the chamber, i also have a 40in barrel, how much should i shorten the chamber, yes it is loud

It would be better if you posted pics

Read up on "CB Ratio" on the Spud wiki;
http://www.spudfiles.com/spud_wiki/inde ... rrel_ratio

For a generic combustion spudgun you want the chamber volume to be 50% to 100% of the barrel volume, that is, a CB ratio in the range of 0.5 to 1.0.

For the original chamber volume, a 2" ID barrel should be 40 to 80 inches long for optimal performance.

If you cut the chamber length in half then the barrel length should be cut in half as well, giving a barrel 20 to 40 inches long.