Pierre,
NEI handtools makes several moulds for the Sharps. I use a Christmas tree
ringtail that is easy to cast and shoots well in my '63 sporter.
I believe you can find the web site at; neihandtools.com.
Hope this helps.
Pierre,
Please go to "Black Powder Shooting" and see ".54 caliber percussion bullets" I use two bullets but so many others used by experienced shooters are listed in various posts here.
Gregg