British Bombs - Construction
British bombs generally are highly streamlined, although the later designs, such as the MC bombs, are parallel sided, resembling the American GP bombs in external appearance. GP and MC bombs are usually of cast, one piece construction, although some MC bombs may be built up in welded sections of cast or forged steel. SAP and AP bombs are always forged in one piece and heat treated for greater strength. The exteriors of these bombs are well machined. HC bombs are of thin walled, "boiler plate" construction .