Controlled pressure casting

A method of forming composite metal castings, comprising:

• positioning a first end of a first structural member in a first mold cavity and a second end of the structural member in a second mold cavity, the first and second mold cavities being fluidly coupled to a reservoir of molten metal;
• applying a main pressure to the molten metal in the reservoir to force the molten metal into the first mold cavity and the second mold cavity until the molten metal expands into the first mold cavity to a first expanded volume and the second mold cavity to a second expanded volume;
• encapsulating the first and second ends with molten metal to secure the first structural member to castings being formed from the molten metal in the first and second cavities;
• and
• applying a first auxiliary pressure to the molten metal in the first mold cavity to reduce the volume of the first mold cavity to a first desired volume and applying a second auxiliary pressure to the molten metal in the second mold cavity to reduce the volume of the second mold cavity to a second desired volume, wherein applying said first and second auxiliary pressures is initiated after sensing each of said mold cavities respectively attaining said expanded volume.