The 7.62*51 & 308 Winchester have the same maximum pressure - 60 191 psi (CIP) / 62 000 psi (SAAMI). I looked at the Never Exceed Pressures for various powders and bullets from 140gn to 175gn and none exceeded the SAAMI pressure (let alone for starting pressures). The L42A1 was proofed for 308W as it is the same as 7.62*51. Whatever killed your range rifle was probably not down to a simple load to specs.