I have a S&B 1-4 with the Flash Dot reticle on my 450/400 double [and one on a Drilling, as well as a Swarovski 1.5-6x42 on a 9,3 double and on another 9,3x9,3x20ga double rifle drilling].

I have not found them to interfere with reloading in any way.

On doubles above 40 cal, If you have problems with iron sights consider a red dot sight.

The Docter Optic shows a lot of promise, I will be testing one in a few days.