Having played with buck in a short Bess, I'll throw out a few thoughts.
First off, remember that buck is just big shot; the same rules apply. Generally speaking, lower velocity=tighter patterns, higher velocity=wider patterns. If you want it to pattern tighter at a relatively high velocity, use a card sleeve to hold the shot together as it travels down the bore. Different shot will pattern differently, whether the shot is hard or soft, different sizes, cast or dropped, etc.
In other words, you may have to play around with loads to get what you want.
Most of my shot was cast, either wheel weights or soft scrap lead. The hard stuff had a BHN of about 20-21 as I recall. I used the water drop technique. After some problems with fusion early-on, I waxed the buckshot by wiping it with a piece of terry cloth filled with Johnson's Paste Wax. No further fusion problems.
Card wads were about as effective as anything. I stuck with Starr's recommendations and used two cards under the shot/one over the shot. Wads were punched out of poster board.
Charges were those recommended for equivalent weights of birdshot.
There's really no reason to string shot on fish line; it is not PC, it degrades accuracy, and takes away the "spread" advantage of shot vs. ball. Besides, piano wire is more effective! (Finally, a fun way to trim brush around the backstops!)
