Thread: Reloading for a double rifle

My old boss used to work for Holland and Holland and has recently acquired one of their fine double rifles in 303 British, I think it's a royal model but not sure, in any case its probably worth several times more than my car. We're going to develop a load for it, it's over 100 years old but at some point the sights/barrels were regulated for modern ammo. Does anyone know how velocity, seating depth, etc might effect the poi for each barrel? Or is it a matter of fine tuning different variables until we get lucky and both barrels shoot the same at 100m or whatever the regulated distance is?