Hi 260 ! Although I never owned a drilling, I heard a lot from other German hunters using them for decades. First, if you want to use slugs, the drilling should be ordered from Merkel accordingly, then it is no problem to regulate them for you. Even better if you name the type of slugs you intend to use. The combination 12 ga / 9,3x74R is fantastic for all-round use, except for the African Big Boys, I'm not sure about Australia's buffaloes. My last advice is to stay away from the German claw-mount, they are almost obsolete here in Gerrmany, most hunters prefer a swing-mount these days, for example a EAW or comparable. When you use a claw-mount and decide to change the scope, It's gonna be VERY expensive compared to a change with swing-mounts.

Wicked good hunting !