Good morning Gentlemen

I hope you are well during these dog days.
I had a question about having a second barrel made for a single shot rifle. The rifle and action are both blackpowder proofed. Is it possible to have a smokeless cartridge barrel made and use it on this action? I was planning on a smaller caliber, but is the limitng factor case pressure or bolt thrust?
The current caliber is 9.3x72r