I heard that at some point after LC took over rolling NM ammunition, though, their management put a stop to that extra testing and sorting, so mixed, non-select lots began to be used and NM ammunition was never as good again. Don't know what year though
Early 60' NM was better than late 60's or 70's. You can look at the data in American Rifleman.
McNamara contracted out the Arsenals and any organic capability in the Government. He started it and it just has got worse over time. The whole Government is contracted out. LC today is a “Government owned, Contractor Operated" facility.
The old Government Arsenals were interested in getting the best product out the door that they could. Contractors are interested in making the maximum profit. When you have LC up for bid, the current contractor runs the facility into the ground to make the most he can because winning the next bid is not guaranteed.
By the time you get into the 80’s LC bullets were so bad that the Government bought Sierra Match kings for the 308 NM ammunition.