I would send it back, and since you mention that this is the third try to get it right, I'd shop elsewhere.
Since you're original question was about a repair, I'll mention something that Peter Alexander wrote about on a swamped barrel that he inleted before he discovered that the breach plug as not properly shouldered to the bore. He silver soldered a piece of (I believe it was German silver) to the face of the breach plug and re fitted the breach. This seemed to me to be an elegant solution, but well beyond the beginning gunsmith level.
Good luck.
Since you're original question was about a repair, I'll mention something that Peter Alexander wrote about on a swamped barrel that he inleted before he discovered that the breach plug as not properly shouldered to the bore. He silver soldered a piece of (I believe it was German silver) to the face of the breach plug and re fitted the breach. This seemed to me to be an elegant solution, but well beyond the beginning gunsmith level.
Good luck.
