Gas turbine ring segment cooling apparatus

A gas turbine shroud ring segment assembly (36) with an outer structural block (32A) having cooling channels (72) between inlets (60) on a front face and outlets (74, 76) on a front hanger rail (48). The outlets may be positioned on a radially inner surface (77) of the front rail for impingement and forced convection cooling of backsides of radially inner front lips (44) of adjacent shroud ring segments (30A, 30B) mounted on front and rear rails (48, 50) of the block. The outlets may enter a pocket (86) on the inner surface configured to allow coolant flow in all positions of the ring segments (32A, 32B). The cooling channel may form a main channel (72A) and tributary channels (72B, 72C). These channels may be drilled upward from the rail to the inlet. The tributaries may have offset intersections (72E, 72D) with the main channel.