I had some scopes and some shotguns sitting in the back of the safe hardly getting used. I mounted a Leupold 4x on a 12ga Mossberg 500 and put in a rifled choke tube. I got a preliminary zero with some cheap frangible slugs I was given, then zeroed it with the premium slugs I plan to use. That saved me money and shoulder pain. I mounted it with a set of Millett rings that have pistol sights on the top half of the rings. I plan on trying some Federal Flite Control buckshot and seeing if that scope is appropriate, probably get to that next week. Then next I'll try it with a turkey choke and birdshot and see what results I get. Ideally I want to be able to keep a scope card and just change settings and verify.
Next project was a 20ga Mossberg 500 and a "Gobblestopper" from Tru Glo. Setting that up as a low recoil buckshot gun and turkey gun by changing chokes. However I found I had less #4 birdshot than I thought when it came time to zero so thats going to wait until after Christmas probably.
FWIW, I was very careful how I mounted the scopes. I degreased where appropriate, used blue Loctite, and made witness marks with a paint pen to see if things were moving. I was also careful to align the Millet rings, they're adjustable for windage and I wanted to make sure there was no stress on the scope from a misaligned ring.