Variable bore ram packer for a ram type blowout preventer

A variable bore ram packer designed for use in a standard ram-type blowout preventer used in oil and gas drilling operations is disclosed. The variable bore ram packer includes top and bottom second plates having a central semi-circular opening which is sized to fit closely about the largest diameter pipe the variable bore ram packer will seal against. Anti-extrusion plates having a smaller central arcuate opening sized to fit closely the smallest diameter pipe the variable bore ram packer will seal are attached to the underside of the top plate by guide screws. The guide screws extend through slots in the top plates which control the motion of the guide screws and hence the anti-extrusion plates as the anti-extrusion plates move and seat against different diameter tubular members. A packer member of elastomeric material having a central semi-circular opening sized to fit closely the smallest diameter pipe the variable bore ram packer will seal is molded between the top plate and anti-extrusion plates and lower plate to form a unitary structure. A radially disposed cavity is molded in the packer adjacent the anti-extrusion plates to minimize damage to the packer as it moves radially and seals against different diameter tubular members.