Most states, no. In FL the "security guard rules" are more likely something the guard company put in to limit their legal liability - same reason they often limit the guards to 38Spl in a 357 gun. IF the limits are found in the law, they're likely only applicable to guards.
But in the case of, say, a family-run convenience store with guns owned by and used by family members and employees, it's basically anything goes in most states. Probably up to NFA-rules stuff if they have the paperwork (full-auto, short-barrel shotguns, etc...yeah, you CAN press that sort of thing into defensive duty, although it's not very smart because the wrong DA might try and seriously twist a jury around over it).