Do a detailed inspection of the gun.
Measure the barrel overall length, the length of the bore inside, the bore inside, the barrel OD at the breech, the barrel OD at the muzzle, the trunion length & diameter, the vent (touch hole) diameter, the thickness of the liner. Take a small bright light & inspect the bore for rust & seams.
Try to see if the bore is centered properly. (Some early repro guns with liners cast in place, the liners got off center leaving one side too thin. Come have reported shining a bright light in the vent, there were able to see where the light struck in the bore.
A picture with ruler of the muzzle, and inside the bore would be helpful to advise.