or maybe like a helical cage with little wheels that press on the tube so the action would be kinda like putting your fingers around it and pulling along the length of it while twisting
A rifle barrel imparts rotation for an already moving bullet, but a rotating rifling would impart movement to a static bullet. Hmm wonder if you could design a projectile launcher by rotating it fast enough.
This idea is interestingly like the duality of e-m fields (moving conductor in magnetic field generates current, varying current in magnetic field moves a conductor)