What comes to mind is that the Oct section won't be very big once you've rounded it. Most Anguish guns have pretty big britches, 1 1/4 to 1 3/8 at the fattest part.
Most English round barrels are filed flat where the lock mates up, and on the opposite side as well. This makes for a nicer barrel breech inlet without gaps and a thinner gun from lock to sideplate.