I didn't think there were set distances; convergence is about regulation; regulation is about dealing with muzzle jump, recoil and the "up and away" recoil continuum, muzzle velocity/barrel time etc. All of these variables are affected by the characteristics of the individual gun and load, and trial and error is the way to get there.
I guess there would have to be some ball park figure to start with though, and a quick and dirty rule of thumb for lower grades which will never be indulged with that time-consuming regulation process.
RG
Possibly on a $100k shotgun that process of regulation is used. The H&H video shows shooting a shotgun for regulation by their guy. I suppose that could be challenged as well, since it's not the buyer that is shooting it nor his loads.
Me? I think that virtually all "production" guns that are not made to a customer as a "best gun", are regulated by dimension and most are not shot by the factory to check regulation.
