In case anyone is looking for a 45 caliber hexagonal mould, Pedersoli has them on sale: (You need to Login or Register to view media files and links)
Tom, are you hoping to get a 50 caliber one?

Tom, yes the PH Whitworth shot cylindrical bullets very well too. I remember that I had to cast them a bit softer than the hex pp. Here's a photo of a selection of the projectiles used. Two types of hex, the round nose version was a tight fit to the bore with the pp version slightly under bore specs to allow for the paper wrap. The bore had to be very clean for these projectiles to work. If BP residue was not removed between shots it was REALLY difficult to seat these bullets down on the powder charge.
As an aside, Whitworth rifling was also used by Westley Richards in many of their breechloaders, though it was octagonal (8 sided). I have a WR Monkey Tail capping breech loading match rifle that is so marked on the barrel. These rifles were used with cylindrical projectiles only and proved to be very accurate. 

Gibbs, thanks very much for the info about making hex moulds, I did not expect to see a copper bullet cherry .
Spud