Thanks to a commenter on last week’s Now That’s A Knife post for pointing out that Jeremy Hanson’s Spudgun Technology Center has a custom machine for rifling PVC pipe to make more accurate barrels for potato cannon. They sell several varieties of rifled PVC (including clear) in assorted lengths. The way I hear it, the rifling machine was first designed and build by STC founder Ed Goldmann. [Thanks, Bryce Bell!]