It sounds like High Standard High Power rifle. These had commercial FN Mauser actions with military-style swing safety and were made in small numbers in .270 and .30-06. Some were sold by Sears Roebuck under their own model number.
The Sears model had checkered steel butt plate, pencil barrel and varmint style for end stock section.
Belgian FN Mauser would have Belgian proof marks and large FN monogram on front ring/bridge of the action.
