Growing up in the Vietnam era, I remember all the cruisers in the small towns around metropolitan Boston used to have the shotgun mounted up front in a vertical position where the radio system now is.
I don't know if because of the lack of use, or because of the increase in the "liberal" population, but it met it's demise years ago.
It took a tragedy, as always does, to get more fire power on the street.
Since that nut Mucko walked into the office in Wakefield, many of the departments in the area now carry AR-15's. I believe this is the most popular cruiser rifle in the nation today.
I know some of the cons they were worried about was liability/security {if stolen} and over penetration. You won't see many in cruisers in the heavier populated areas of the state because of this.
In these areas, they seem to be reserved for swat teams.
My opinion...give street cops everything they can get their hands on.