Can any one help with information on this bullet. It weighs approx 490grs, approx .454in (11.55mm) dia, 1.46in (37.36mm) length and has a paper sleeve with "Whitworth Patent" written in old fashioned writing. At the base is a leather or felt disc with a thin metal disc with 6 small holes in. I can find general info and photos on whitworth bullets but not one that looks like this. If any one can help it would be appreciated. The .22in rimfire is for comparison.