What kind of barrel does the Brown Bess musket use compared to an octagon rifle barrel?
The barrel is mostly round, large at the breech, and tapers down, likely with some belly rather than a perfectly straight taper, since it does not flare much given the bayonet needing to sit fairly straight at the muzzle. It is a thin-walled barrel, more akin to a fowler barrel than an octagon rifle barrel.