What causes case head separation? I'm shooting a TC Encore pro hunter in .308. My loads are 45gr of Varget, Winchester LRP, and Winchester brass, shooting a 165gr nosler ballistic tip. I've shot about 30 rounds of this exact load with no pressure signs, etc. yesterday at the range, I shot 10 rounds, and had one case wad totally separate, and three others crack in the same place. It was about 15 degrees warmer than the last time I shot. Also, this brass is somewhere around 20 years old, and has been reloaded "maybe 3 or 4 times" according to the guy that gave it to me. Is it just worn out brass, or should I look elsewhere?