You will be spending more on those shotgun/muzzleloader scopes. Get yourself a quality Leupold VX-II, for me I like the 3-9x40.
It IS a scam...the only realistic difference other than secondary features is marketing. While some features may be different for each model, there is no inherent difference that makes any scope a MZ, Rifle of shotgun scope.
For examlpe...parallax can easily be changed by the factory in any scope..that does not make one a rifle scope and the other a shotgun or MZ scope...also eye relief can easily be altered, (increased/decreased), in the design process of any scope, at the cost of a smaller field of view, (when relief is increased), this does not make one scope a slug scope or MZ scope instead of a rifle scope...also any reticle can be put in any scope, whether the reticle matches the trajectory of a specific projectile doesn't mean the design of the scope is any different whether it be a slug, mz or rifle scope.
Moral of the story..in the majority of the cases...most of your money is being wasted when you pay more for a "MZ scope" or a "slug scope".
Instead of buying a lower quality over hyped dedicated slug or MZ scope...put your money into a similarly priced standard rifle scope and you will have a higher qulity scope that will rewarded you more in the long run.