I looked at the two Perazzi guns I currently have, a MX8 and a DC12. Both have blued actions and have been shot a lot so it is easy to see where the bbls bear on the action due to blue wear. Both were bought new, are still tight on the face w/ the top lever well to the right & have never had any adjustment on the bbl to action fit since leaving the factory.
On the MX 8 the back of the top barrel bears on the face of the action from about the 9 to the 3 o'clock position & there is no indication of the monoblock bearing at all on the flats that is visible from the blue wear.
On the DC 12 SxS both barrels bear from approximately the 8 o' clock to the 4 o'clock position including the rib between the bbls & approximately .200" of the front edge of monoblock is bearing on the action flats.
As mc posted, I don't see how you can keep the hook tight against the hinge pin (for long) unless the back of the bbls are bearing against the action face.
