I think it would just take someone who understands lining to just measure the the candidate barrel. I don't think this is a situation where a .410 shotgun barrel is being converted to a rifle. It is more likely that a roughly .25, .30 or .38 rifle is just being lined to original or similar bore and groove. The only difference is that at some point a decision was made to leave it at a .410 inch smooth bore for a while.