Surplus LC 7.62X51 brass weighs more than commercial .308 Winchester brass. The internal case capacity of LC 7.62X51 brass is less than .308 Win brass, hence loads that are safe in .308 Win brass must be reduced in 7.62X51 brass to retain the same pressure.
I weighed a couple of pieces of 1975 LC NM brass today that was ~20 grains heavier than WCC brass of about the same vintage.
Surplus 5.56X45 brass weighs the same as commercial .223 Remington brass with one exception; PMP brass weighs about 10 grains more than the rest. LC, Lapua, Winchester, Remington, WCC, and so weight from about 92 to 95 grains. The walls of LC brass are not thicker than that of commercial brass.
Reduce the loads in PMP brass to maintain similar pressures produced by the load in LC or other commercial brass.
Occasionally check the weights of commercial brass, and LC for that matter, to monitor changes.
Every reloading book in print contains incorrect information about 5.56X45 brass. Whether it does or not isn't relevant anyway, we all have to check and confirm the details for ourselves. Reloading is all about the details.