Breech block hanger support

A breech block hanger support member for a subsea wellhead assembly for wells having a working pressure up to approximately 15,000 psi. The assembly includes a wellhead, the support member, a packoff for sealing the support member, and one or more other casing hangers supported by the support member. The support member is connected to the wellhead for itself suspending casing, for supporting at least one other casing hanger and casing, and for containing the working pressure. Breech block teeth are provided on the wellhead and support member to permit the support member to be stabbed into the wellhead and rotated less than 360 DEG for completing the connection therebetween. The teeth include groupings of spaced-apart no-lead teeth having slots therebetween. The slots provide a flow way for passing well fluids. The support member further includes an upper annular flange for arresting its downward movement within the wellhead. This flange includes flutes aligned with the slots for passing well fluids. The support member includes threads for connecting to the top of a casing string. The upper surface of the flange provides a bearing surface for supporting another casing hanger. The bearing surface of the support member will support all of the casing and tubing load and contain the working pressure. The bearing surface between the breech block teeth is greater than that provided by the support member for the other casing hangers. The packoff seals the support member with the wellhead and other casing hangers.