Unless its been changed out , the flip up sights on a Pedersoli , are meant to be for distance not for individual barrels.
On a true express rifle , the barrels are regulated by a wedge . This allows both barrels to be adjusted to hit at the same point of aim at distance .

With the Pedersoli and the CVA models , normally they are not regulated very well and they are not adjustable . Because of this a lot of times folks will change out the standard sights for a set of express sights . Which it sounds like you have . IE two flip up rear fence type of sights . One blade is then adjusted for one barrel and the other fence adjusted for the other barrel .
However if you don�t adjust the sight , one will be for closer �low fence � and one for longer distance �taller fence � . that�s why your shooting high as you using the taller fence for one barrel .

Try shooting both barrels on the shorter fence . They should hit SXS or very near the same hole . Then move your distance out and use the taller fence with both barrels . They should hit close to in the same spot consistently .
If not , then you will have to adjust the rear sight so that each fence is for its own barrel

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