Raimey,
I have never seen such porting on a double rifle, in fact it seems to have been done with common gunsmithing/machine shop equipment instead of EDM. The Scope seems to be a recent addition and mounting a scope on a double rifle is pretty commonly known to change the point of impact of the bullets. A possible intention of the ports would be an attempt to correct "regulation" of the barrels. The cartridge the rifle is chambered for is not known to generate enough recoil to justify porting for that reason, plus the ports do not seem to be located to control " muzzle whip"(vertical). The location seems to be an attempt to correct regulation of a rifle shooting "wide", as opposed to "crossing". Only shooting it will tell the tale. As always, I may be wrong.
Mike
