The Bead front sight on that gun is NOT a very good sight to use for shooting RBs accuracy, IMHO. And, being centered, you have the added problem of regulating the barrels to get the balls to hit at the same point of aim at some chosen distance from the muzzle. Most of these CVA guns were never meant to be used with RBs. They are not regulated for Shot loads, much for RBs.
I would first try shooting RBs out of each barrel to see what kind of best group either will fire. Only if I found at least ONE barrel shot RBs accurately out to 50 yards, would I bother tackling the sight issue. Where the Balls impact will largely guide you on how to solve the problem of choosing the right kind of sight.
Don't get the cart too far ahead of the horse with these kind of projects. They will be frustrating work for you enough, just approaching the work systematically. :hmm: :thumbsup: Your CVA shotgun is NO KODIAK double rifle. Its not built from strong materials, nor are the barrels the same weight and diameter you find on the Kodiak. That doesn't mean it can't shoot RBs from at least one barrel well enough to take Whitetail deer, but it does mean that you need to focus on finding the most accurate load, rather than the fastest load. A 12 gauge ball is going to pass through any whitetail you are likely to shoot. :shocked2: