gunman,
I don't know where you got the idea that shotguns aren't regulated, but they are, or at least they should be. Not to the extent that double rifles are, certainly, but regulated nonetheless. What regulation means, in regards to a shotgun, is that both barrels put their respective patterns to the same point of impact at a certain distance from the gun. Getting the gun to shoot to point of aim, or where you are looking, then becomes a matter of fitting the gun to you to make it do so.
I will not tolerate a shotgun that does not print both barrels within 2" of the same place. I can live with 2", but no more. I recently was given a new .410 double built in Turkey. First thing I did was pattern it. Right barrel prints to point of aim, but left barrel prints 4" right. This at 25 yards. This WILL be corrected, or the gun will move on.
Your ideas about barrel joining lead me to believe that, if you did indeed build guns, you must've been a stocker, checkerer or engraver. I certainly wouldn't want a gun you had joined the barrels on.
SRH
