We have all picked up numb guns that have had less life than a plank of wood. Just as we have held guns that feel alive , almost if hey are eager to get on you shoulder and shoot .I know the old adage about balance on the joint pin on a side by side , but so much will depend on the length of the bar ,length of stock and of barrel that I cant help feeling this is one of the old tales used by salesmen such as the correct length of pull is the distance between the first joint of the fore finger and the crook of the elbow , to persuade a customer that the gun is right for them.
This balance point can not be related to an O/U . Guns with multi choke are inevitably barrel heavy by nature . Balance to me is how the feels between your hands prior to mounting, how lively it feels to you ,which may be different to how it feels to me , how it feels on you shoulder . It is an undefinable quality that will differ to each of us .