A "split case" means little, especially if you mean a split neck. That happens with brass fired more than about 3 times, due to the brass getting brittle--or case-necks the factory somehow failed to anneal after forming, which is necessary due to work-hardening of the necks during forming
That can happen. One example I've mentioned several times is the batch of 7mm Remington Magnum cases Charlie Sisk bought several years ago. He was getting lousy accuracy from the rifle he'd just built, so called me. Eventually I suggested he might try annealing the cases. He'd never annealed any brass, so I told him the "candle method." He tried it, and the rifle then shot half-inch groups.
Split necks have nothing to do with pressure.
