Mike,
Maybe coffee time, but a gun with a heavy breech and light muzzle has built -in elevation. :-)
Still, with a shotgun, look Over the breech, keeping the head upright if the cast allows this, and use the front sight if you wish, or just look at the target and forget the barrel altogether. If this still produces low centre of pattern, then yes, bend the barrel a bit. My 44 " 16 bore needed an upward bend to work well.