Question:
Upon examination of the barrel and noting right away that its length was incorrect why did he accept it?
Away Alarm Bells should have sounded as the closer he examined the barrel the more discrepancies he noticed.
He does have however some viable alternatives legal or otherwise.
After talking with this gunsmith and getting nowhere fast, retain legal Counsel, Contact the BBB, & Post information about this incident as well as the company and owner's name on as much social media as possible ( include all photographs and all documentation ) .
Additionally by word of mouth, being certain to back up your allegations by keeping at hand all documentation and photographs to present if need be.
After all one picture is worth a 1000 words.
Perhaps if you told the so called Gunsmith who sold this to you about his shoddy workmanship as well as what your intentions now are he may reconsider and make things right.
After all nobody who is reputable would want such a stain on their name or business ,as in the long run it can ruin both his name creditability, and even his practice .
All this should provide food for thought.
As to your firearm
Danger :
Please do not attempt to use with this barrel in place!
Good Luck!