PISTON SEAL RING

A split ring seal (102) has: a first circumferential end (124) and a second circumferential end (126); an inner diameter surface (128) and an outer diameter surface (130); a first axial end face (132) and a second axial end face (134). The outer diameter surface (130) has a sealing surface (222). The first axial end face (132) has: a first section (244); a second section (246) outboard of the first section (244); and an axial protrusion (242) between the first section (244) and the second section (246). The second axial end face (134) has: a first sealing surface (225); a second sealing surface (226) radially outboard of the first sealing surface (225); a circumferential channel (228) between the first surface (225) and the second sealing surface (226); and a plurality of channels (230) extending radially outward from the circumferential channel (228).