.303 cartridges were not loaded with mild steel cores. Invariably they have a lead alloy core with fibre or aluminum tip. If there is a steel core, it will be hardened, and the round will be an armour piercing one. In .303 headstamp codes, B is blank, G is tracer, P is incendiary, and W is armour piercing. British and commonwealth .303 cartridges were invariable loaded with two jacket materials; cupro-nickel - silver coloured - and, guilding metal, copper-zinc - copper coloured. .303 ammunition may have been made elsewhere with copper coated steel jackets. It is not uncommon for full metal jacketed bullets to be referred to as steel jacketed bullets, even though they are not.