Grade O top lever Hammer 16 with 34" barrels

[Harold Pickens]

Surprised me, just figured it was on a 1 frame, but measures exactly 1 inch between pins.
Bores are still rough--but better. Used a wire bore brush, then wrapped a 20 ga brush with a scotchbrite piece soaked in Hoppes 9, and put cleaning rod in a drill. May do a little more
today. Just snapped barrels onto the frame, and they are way off face.

[Harold Pickens]

Off face

[Bill Murphy]

Looks like someone ground off the breeches on a wheel or a stone. Try those barrels on another 0 frame hammer gun to see where the metal is missing or worn.