Board takes up ban on gun sales Law would prohibit selling high-powered rifles in unincorporated areas By Tamara Grippi, STAFF WRITER MARTINEZ -- High-powered rifles are the target of a new ordinance that will be introduced by the Contra Costa County Board of Supervisors at their meeting Tuesday. The proposed law would prohibit the sale of .50-caliber rifles in unincorporated areas of the county. Supervisors John Gioia of Richmond and Gayle Uilkema of Lafayette, who are recommend-ing the ordinance, say the ban is intended as a public safety measure. Telecommunications towers, industrial plants such as oil refineries and railroad cars...