My Dear Wrangler -
By all means, please follow Monsiuer Kids' link as it is a wealth of info regarding these amazing gadgets.
As an owner/tinkerer of an IAB 1863 business rifle I can attest to the ongoing maintenance issues!
If you obtain a version that has the floating chamber, you will find that the chamber is a project unto itself, especially trying to keep it "floating" , unless it has already frozen itself in place.
The self adjusting breechplate usually is not self adjusting until you free it from its breechblock constraints, relieve some of the metal to allow it to slide, and then perform the Historically INcorrect "Rubber O-Ring" fix.
Once you have performed those outwardly apparent chores, you will want to remove the breechblock cleanout screw, and examine the fire channel to ensure it is free and clear pf unwanted metal scraps.
Lastly you will want to dissasemble the works completely, and examine all moving surfaces for burrs, & etc, tune tohe lockworks, and re-harden surfaces as required.
Pedersolis will take less tinkering with the lockworks.
Now that you have finished your "kit" you can purchase the $100 perdersoli mold to cast the correct-fitting "400 and some" grain Sharps Christmas-tree Ringtail bullet, drop one in, and follow it with 95 grains of loose powder (in the .54). When you recover from the bruises, you will probably want to continue with nitrated paper cartridges using from 50-70 grains of powder.
They are great fun for someone who enjoys tearing down clockworks and such, and for one who is not looking for accuracy better than "Minute of Coffee Can" at 250 yards.
hope this helps
yhs
Prof Marvel