Currently working on an old Khyber jezail with an original British Brown Bess lock. The bore is Afghan pristine.... crude polygonal rifling somewhere between 51 cal and 62 caliber and full of sand, rust and spiders
The barrel is Persian damascus. The lock/trigger appear to be fully functional and are now soaking in solvent along with the bore. Once cleaned and all tuned up I'm going to give it a go with a patched roundball over a light BP charge.
If I can get the thing to spark there will be holy smoke for certain just not sure where the bullet will go. Will try .50, .52 .57 and .61 fodder. With that type of extremely deep rifling it is difficult to say which size may work best.
Will, report back on results.