Combination guns are a compromise. Always have been, always will be. But they are incredibly useful.

No reason why you cannot use the shot barrel with the scope in place. Especially on ground game - rabbits, foxes etc. stationary / slow moving shots are no issue. Moving or flying shots practice is needed. Watch the target, concentrate on the target and point the gun keeping both eyes on the target and squeeze the trigger. A low powered scope helps, but surprising what you can do with a 6x scope.

Mine has a claw mount - monstrously expensive if having fitted these days - so easily removable, but if I am using it as a rifle then it stays on. I have shot plenty of things with shotgun barrel with the scope mounted, but mostly its close range foxes, squirrels etc.

If / when I go after birds, scope comes off and only shot barrel is loaded. (I don’t want to accidentally send a bullet into the next county when trying to shoot a duck). I always have a rifle cartridge in my pocket and can happily use the open sights if needs be. Or typically I go out for a Roe Deer, nothing turns up and then stop by duck pond on way home. I have also had no luck after a red stag, but are a few grouse in the heather - but never got close enough!

I am confident in the return to zero of the scope, so if needs be I can always replace it. But open sights good enough for 50 to 100m shots if needs be.

I really like the idea of the 412 system. It does give you lots of options and a very good travelling gun. With the 12 and 7x65r you pretty much can take anything. But you have a double shot and a double set of barrels if needs be.