Brass jacketed .303 bullet

I have a .303 bullet that came from a round that had been highly polished (hstp I presume means nothing, it was one of those fired cases with a bullet fitted you get in the UK). The jacket looks to be brass, as it was copper-coloured below the case mouth. It looks as if the copper plating has been polished off. This bullet has a flat base (no boat tail) and a lead core. It does not take a magnet. The OAL is 1.285". It has a curved concave cannelure 0.45" from the base. Is this a standard .303 British bullet? and is it actually copper-plated brass? (Why not just leave it plain brass?)


I have now decided this is not brass. The colour of the metal has just changed slightly where it has been polished, so it looks almost like brass.