canada,
I've used and reloaded 7x65R in O/U doubles here in OZ.

Couple of questions.

Firstly what distance are you shooting at?

Are you shooting with scope or open sights?

How are you steading and holding the gun during shooting?

Is 5 inches the best it has shot?

Are the barrels shooting apart by 5 to 8 inches or are they crossing?