RE: Using a red dot on a slug gun.....
I have a Bushnell Holosight on my Nova Rifled Cantilever, and one on my son's 870 20ga, rifled barrel, saddle mount. Practical, fast acquisition, and where the dot is, the slug goes. A red dot would by my second choice. The Holosights are pricey, but I got both of mine at good prices on ebay.