First, shooting from a bench rest will throw the regulation off. I would expect the gun to cross fire from a bench rest.
The proper method is with a standing rest. Since they are not widely available use a pair of shooting sticks with the proper hold. The gun must not touch any part of the rest, your body must be free to recoil. Try this before you say the regulation is thus and so.
Also, proper regulation distance for shot guns is 30 yards for 410 and 40 yards for all gauge sizes. It's not a rifle, don't expect centers to be within a half inch at 40 yards.
