When I started reloading for the 260 Rem in 2007, I used Remington brass from the rounds that I had fired. It was dire with different batches showing a case weight variation of in excess of 5 grains. I used to sort it into batches with a 1 grain variation in case weight. When Nosler brass became available, I leapt at that. Nowadays, I only use Lapua brass. I would suggest given the current costs of reloading components, that you select one type of quality 260 Rem Brass and buy as many cases as you can afford?
Good luck.
JCS