I have had a few combination guns, a scoped 30-06/12ga, a scoped 7x65R/12ga, and an unscoped 7x57R/16ga. The 7x65R/12ga combination was by far the most versatile and I used it for pheasant, dove, pigeon, and deer.

I cannot image trying to shoot a shotgun using a scope. Any magnification would severely limit the field of view and even a 1X scope would make it very difficult to keep your eye on the target. The only exception would be when shooting a stationary target like a sitting rabbit. And how would you ensure the scope is regulated for both the rifle AND the shotgun simultaneously? Maybe it would be, but if it wasn't that wouldn't be very good at all.

I have never seen a swing away mount that any good. They are awkward and make the weapon feel out of balance, even on military rifles. I cannot imagine trying to shoot a shotgun with one of those contraptions mounted on it.

My combinations used EAW type swing out mounts. A single lever at the rear is flipped and the scope rotates out of a dovetail in the front. Installing the scope is just a matter of reversing the procedure. Those mounts are simple, fast, and do a great job of retaining zero.

But here's an idea. Why not mound a scope and then put a small reflex sight on one of the rings. Rings and ring halves are available with small rails on them. They make it easy to mount a red dot reflex sight like the Burris Fastfire 3 or the Vortex Venom on a scope.

People are already using the small reflex sights with their shotguns......

... and many rifles have a little reflex sight on the scope so the shooter can quickly transition to a red dot in a CQB situation.

So, why not mount your scope in the usual way and add the reflex sight to it? Then you could shoot the rifle or shotgun at will without removing or changing anything. Furthermore, each could be adjusted to shoot where it should.