In a muzzleloading gun without a choke, oft times the cushion wad will attempt to plow through the shot column after it leaves the bore, thus making the gun shoot wide patterns a large, or several large holes in it. ie: not even.
As Mike noted, you can adjust shot and powder charges and at some point, will find a combination that will shoot very well, using a standard wad column. Taylor also did this with his Manton which is not choked.
Modern guns benefit from plastic wads, which prevent much scrubbing of the shot in the bore- however if used in BP loads, can coat the bore with melted plastic. That is not something you want.
If you want to use plastic wads, these will help tighten patterns, however put a tight hard card wad between the powder and the plastic, then an overshot card over the shot. You must experiment to see what works
in YOUR gun. some guys use rolled post-it note pad paper as a shot column sleeve, while others have good results from using bank coin wrappers as shot concentrators.
In the 1800's devices were available for concentrating shot for longer range shooting. These had different colour wrappers for different ranges. Some guys have noted, that at close range, their
shot containers shot like slugs, however they did not attempt to use them past 25 yards, where they might have worked perfectly, as with the shot containers made for muzzleloaders, many years ago.
Now, as far as I know, these 'shot containers' were not made in the USA, however they were quite likely imported and most certainly were used here by visiting sportsman, ie: Englishmen as accounts of their use is a part of US History, as re-counted in Firearms of the American West.
Here is one such:
