I make up the paper cartridges for my Pedersoli Berdan Rifle because it’s less messy overall and also because loading with loose powder seems to aggravate the incidence of gas cutting in the breechblock, at least from the reports I read.

But those who do use loose powder just dump the 50-60 gr worth behind the bullet close the lever, cap and fire.  Even with a paper cartridge, there is plenty of empty space in the chamber and breechblock cavity.  If you filled the chamber with loose powder, it would fall back into the block cavity when the breech is closed, so there would still be an “air gap.”  I’ve never heard of any chamber ringing phenomena associated with this practice.

You might research the “1863 Support Forum” on the Shiloh Sharps site and also the appropriate forums on the N-SSA site.  Plenty of info there on the management of Sharps percussion guns.

It is well worth the effort to roll your own paper cartridges.   Just works a lot better.   I nitrate my paper and roll tube tight with the bullet, glue it with tacky glue which dries very quickly.   Then pour in 60 or so grains of powder and glue a disc of cigaret paper in the back end.   I make my tubes so that they come right to the rear of the chamber.   It sounds like a lot of work but it goes pretty quickly once you get the hang of it.
I shoot an original carbine and a Shiloh Infantry Rifle and they both do well this way.   I never had much luck with loose powder.

George