Rifling Spud Guns - Follow-up

So I glued some felt onto one of the 12ga darts I made for the 1" barrel, and fired it to test the rifling. I have to report that is spins right smartly with a twist rate of about 1:24. There was absolutely no evidence of coning on the flight which probably helped the penetration go more smoothly.

The dart was painted in black and silver to make spotting easier. The black shell is the "before" picture for the darts. Flaring the open end helps the velocity as it greatly reduces leakage. Adding the felt accomplishes the same thing. The felted one was fired at a modest 20 psi and a range of 12 yards. That's 1/2" plywood it's sunken into. An un-felted dart was found to have traveled some 175 yards at 65 psi so I imagine the felted one would make over 200 without much trouble.