Ok so 3" sch 40 is good for chambers, right? also purple primer + regular Oatey pvc cement is fine if I don't care about looks?

Hmm, I was thinking like 1.5 but mebe ill go 3" since i have that lying around anyways. (Just build new house and did plumbing ourselves so lots of leftover pvc )

I'm planing on making my first cannon and was just wondering if there was a rule of thumb for sizes of chamber to size of barrel. I don't mean the volume ratio but I mean like you have a .75" barrel, what size chamber would people sugest? or is it trial and error?