Gorgeous.
Okay, why neither coned nor round bottomed?
some say round bottomed grooves make for easier loading, but IME that has never been the case with 3 totally different rifles, and builders, i've owned and used. round bottomed rifling does increase the depth of the rifling and that typically will require a thicker patch to fill the deeper .012" grooves. i truly believe that the old school shallow square rifling of .008" or .006" is simply better - at least for me, as a result of my personal testing with .45, .50, and .54 rifles.
some say coned muzzles make for easier loading, but i've never found that to be true with the pair of rifles i had muzzle coned. unless the coning is accomplished to perfection, the results could easily be decreased accuracy.
i can only echo what john has posted as to guns made by mr. jackie brown - just say NO. having commissioned him to build me a .62 smoothbore, which was a very far cry from "right" the day i received it, i spent countless hours and dollars fixing what he did, and documented the whole affair in making a truly bad gun into a truly great gun. SO, i'd suggest avoid jackie brown guns like the plague.
there are Many really good builders out there and my current go-to is jim kibler, though i prefer to just buy his kits and do the build myself.