Another Lyman shotshell book of mine lists the wad-attached Breneke's at 1,570fps using Herco powder at 10,700 and 9,700LUP. That's the 575gr., BTW. One must reference the books to see what wad columns they used, as different wad columns develop different pressures.
: As noted above, round balls work just fine in choked guns, as long as the correct size is used. Our testing showed better accuracy with round balls than any slugs - and of course, much better penetration. The key was using the cups from the bottom of (range pick-up) shot-cups to hold the ball in the centre of the bore.