Probably was hexagonal. Some of the old target rifles had a hexagonal barrel. The WhitWorth rifles were well known for having hexagonal barrels. And were extremely accurate rifles.

You can go to Buffalo Arms and see the hexagonal bullet molds. My WhitWorth(replica) is not a hexagonal bore. But I have also seen reproductions with the hexagonal bore. Mine is a 3-band.

I have a real good friend who uses it as his Civil War rifle when he goes to the skirmishes. He has a blast at those re-enactments. They also shoot live rounds at some of the ones he goes to. And that is why he likes my WhitWorth. It is a shooter. I cast a bullet that is well over 400 grains for that .451 caliber rifle(can't remember the exact weight(too early)). Tom.