gabeb123 wrote:good point.
hey so i got a 1.5"pvc barrel that is about 4 feet long and a 3" chamber that is 33 inches long is that good
If good means efficient, no.
Cut the chamber down to 12"-15", that's all you'll need.
For very low pressure stuff such as 6-10 PSI, the ratio is good and effecient. For very low pressure cannons, a very fast valve is not required. A well lubed ball valve provides good flow.
If you intend to use higher pressure then a smaller chamber will be needed for high effeciency. Use GGDT to model your chamber and barrel at your working pressure. An oversize chamber can provide a small velocity increase at the expense of using more than twice the air. For hand pumped stuff, smaller is much less work to pump up.