A method of manufacturing an integral reverse buckling fluid pressure rupturable apparatus comprised of a support body formed of a ductile material having opposite ends and having a recess extending inwardly from one of the opposite ends, the internal terminus of the recess being positioned in close proximity to the other of the opposite ends of the body or to the terminus of another recess extending inwardly from the other of the opposite ends, whereby a relatively thin integral concave-convex rupturable portion is formed in the body having a known reverse buckling rupture pressure.