I reload .303 British cartridges and have been using PPU brass because the cases weigh more than cases made by some of the other cartridge manufacturers. From my own experience - 3% heavier than Remington Core-Lokt and 9% heavier than Winchester Super-X. The basic thinking here is the heavier weight translates to slightly thicker walls of the PPU case which should hold up better/longer than thinner cases if the cases are neck sized only and fired from the same rifle. The PPU cases I've fired show no sign of excessive stretching after multiple reloading.
Does anyone have any fired Mk 7 .303 British cases on hand? I'm curious to know how the weight of a Mk 7 case compares to the weight of a PPU case (in grains).