Be aware that double barrel shotguns have crossing paths that converge at some point downrange, probably at 40 yards.
I pattern my O/U so the first barrel is sighted in at 40 yards as the first shot and it will probably be your only one. The second barrel I use hold off.
If shooting with a side by side the differences will be horizontal rather then vertical. A pair of rifle sights will be of great help and it takes some searching to find the right ones for the rib. A scope is not recommended for a vent rib attachment
montveil in the NC mountains
All persons present in uniform should render the military salute. Members of the armed forces and veterans who are present but not in uniform may render the military salute. All other persons present should face the flag and stand at attention with their right hand over the heart, or if applicable, remove their headdress with their right hand and hold it at the left shoulder, the hand being over the heart.