The originals shot bullets rather than balls, the bullets came c/w powder wrapped in greased paper, you simply stuck it in the chamber then rammed. Except Adams who wrapped in metal foil, you had to pop the back end off to expose tissue paper beneath.

OTOH, original chambers were tapered to give a tight fit, repro's are cylindrical. Don't ask me why. You know you have the right bullet mould for an original when the bullet tip is a perfect fit in the end of the rammer.

I'm not a great believer in flashover at the front. With the cylindrical chamber you should shave lead on loading and get gas tight. IMHO multi cylinder discharges, very rare, are much more likely due to caps coming off and flashover at t'other end. Any grease you plaster in there will all come out with shot #1 and make an icky mess.