Definition of an 'ault Weapon' in Maryland?

Hello does anyone have any resources about how maryland defines an "ault weapon"? My father was going to buy a mini 14 today (law enforcement version with the flash-hider and bayonet lug--- he has a folding stock conversion kit he bought pre-ban at home) at a gun show for a spectacular deal but the only thing holding him back is that he does not want to have to register or get into trouble with it. Im looking for some government sites in particular, it has been much harder to find information than I thought any quick help would be appreciated!