County studies, readies rifle bill By Peter Felsenfeld CONTRA COSTA TIMES All it would take is a willing mind and a powerful explosive to turn Contra Costa's hulking oil refineries into giant chemical bombs. In an age of terrorism and readily available weapons, neither prospect can be completely discounted. So Contra Costa supervisors are scheduled Tuesday to take aim at a readily available gun they say presents just such a threat. The board is expected to ask county attorneys to draft an ordinance that would ban the sale of .50-caliber BMG rifles in unincorporated areas. The measure would be based...