Get a large pot and boil water in it. Then submerse the ABS (with some out so you can get it back) in the hot water and let it sit for a little while. Pull it out and mold it by hand. Try it with junk ABS first so you can get the hang of it. That's what I'd guess, it works for PVC. Don't know about ...

the rifling on potato cannons works because the fins on the projectile have, for all intents and purposes, zero effect on the actual spinning of the bullet. the rifling gives the bullet a spinning momentum, so it keeps spinning because of momentum physics, not aerodynamics. a good example of this fo...