I don't even know where to start on the questioning. Obviously, more information about the rifle is needed. Without that, I would say my Greener doubles have an effective range between 3yds and 300yds.
-------------------- He who lives in the past is doomed to enjoy it.
Please post some photos of your Greener SxS double rifle. What caliber? What load was it regulated for? How accurate is it? What game are you hunting with it?
I look forward to seeing your rifle here on the site.