A centre fire rifle scope, designed for a rifle, almost always has its parallax set about 150 yards. If it is designed for a rimfire, more like 50 or 60 yards. If you look at scopes advertised as a "shotgun" scope, find that specification and see if that is suitable for the use that you have in mind. Certainly a scope that can take repeated firings from a bigger rifle - 338 Win Mag, 375 H&H, etc. will live well on a shotgun - most scopes, however, will not, especially "budget" priced ones. I think most "budget" scopes designed around minimal annual use at the 308 Win - 270 Win - 30-06 level of recoil - probably 95% or so of the rifles that are fired in a year. They would likely work fine on a 12 gauge slug gun, until they don't.
For comparison - the late Finn Aargard's 1948-ish (?) Model 70 Winchester in 375 H&H (bought by him as a used rifle in 1969) is still wearing the same Weaver K2.5 scope that he had installed when he bought the rifle. In the article he wrote after moving from Africa, his notes show over 2,000 rounds fired in that rifle. His wife, Berit, within past five years, used that old rifle and scope to take the rifle's 50th Cape Buffalo. I doubt many shotguns would break a scope like that one.
