Im no metallurgists, but if the cylinder is undamaged, no bullets stuck between the cylinder and forcing cone in the barrel, barrel missaligned etc.
The only times Ive seen this type damage on a new or rebarreled revolver
was caused by barrel overtightening .Pinches ( constricts) the barrel down right in that forcing cone area. Having many custom revolvers, and rebarreled revolvers over the years I always check for this as it kills accuracy. Smaller caliber guns get away with it without much damage but the larger caliber ones it shows up rather quickly. May not be reason but my .02. Good luck Bob

You have to use a match or other tight gauge, range rod head to feel the tightness