As roundball indicated, all guns are different. You have to find what works in yours, Sonny.
With a cylinder bore, you have a situation that isn't present in a choked gun. With a choked gun, there is no constriction close to the muzzle to retard the bad at the last instance, to allow the shot cloud to get out in front of the wad. The result is the muzzleblast pushes the wad into the shot column, spreading it and even causing the gun to shoot a donut pattern. That is normal. YOu have to adjust powder charges, powder granulation, shot charge and wadding to see what works in your gun. There is no one formula - even with a modern shotgun or choked ML gun.
Some guys have good luck with shot sleeves, others not. Antoher trick is to use only overshot wads, like 2 or 3 over the powder, no fiber cushion wad, then the shot, then a single over-shot wad. This pattered fairly well with 1 1/8oz. #8's in an 11 bore H. Whall original ball and shot gun I used a couple seasons at Hefley Creek rendezvous for trap shooting - patterned well enough to win. That system is certainly worth trying.
Another is to use a tap that is just about .010" larger than the bore and turn a 1/2" or so of threads right at the muzzle. This was tried with ctg. smoothbores, but did not work for long, due to the threads plugging up with fouling and becoming smooth. With a ML, they are being cleaned each time you load the gun, so they would remain rough to the oversized wads as they are trying to enlarge all the way out-then when hitting the threads they'd be held back just as if hitting a choke. This would retard the wad at the muzzle as it's design says it will and achievd much better patterning.
I haven't tried it myself, as my gun has a choke, but logic says it will work. It actually worked in Ctg guns for a few shots, so should work as well in a ML for every shot. A twist/wipe with a cloth wrapped finger would clean it easily.
There are lots of 'tricks' you only need to figure out what works for you.
