Remington Unprimed Brass Cases 257 Roberts (50pk)Remington cartridge cases are carefully drawn from specially alloyed brass to provide consistently exact internal volume and resistance to case stretching and brittleness. Primer pocket tolerances are held to . 001", and closely monitored case neck annealing ensures easier re sizing and longer reloading life. New, unprimed brass. This is not loaded ammunition. Bulk brass should be full length sized, trimmed and chamfered before loading. Preparation: