Always - always - always, use a long enough starter shaft that puts the ball down the bore past the front sight dovetail. If you screw up and forget to seat the ball on the powder (not good - ever), and shoot it only short started, it might not ring the barrel. I've seen that (non ringing) happen, even with thin walled smoothbores several times. If the ball is sitting under the front sight dovetail, it will ALWAYS ring.
If rung, the barrel must be cut back and re-crowned. The metal is actually stretched at that point and torn in the bottom of the 'groove' of the ring. We've sectioned several - always the same - torn steel where it stretched.