GLOC depends on many things, mainly on how well person is resistant (pilot's height is one of the main factors), pilots physical state, the protection (g-suite), techniques with which one fights g force (breathing, contracting the abdomen etc), and of course the inclination of the seat. When I was tested before I was enroled in the air force, I could withstand 5.5 g before GLOC, without training, g suite and special training. Later when flying, 7.5 G, just using g suite.