The issue is friction trying seat a large round ball properly onto a powder charge from muzzle. If you have ever seated a patched .50 cal you know how hard it can be. A .50 cal ball has a circumference of . 618 and that is the area in contact with the walls of the bore to set up the friction you are pushing against.. A 1 inch bore has a circumference of 1.237" a far larger are of contact for friction to be induced. Any fouling, debris or imperfection in the bore or ball is going increase friction and make more difficult to seat the ball fully and uniformly on powder charge.
That of course is for a muzzleloader.
As a person who has had a lead projectile hang up in a loaded bore, due to imperfection on the slug of a 1 inch gun, you do not want that to happen.
For a breech loader you are going to need to assure that your patch extends beyond the circumference, to in front of the ball or its likely to "rumpled" loading and make a flyer on target.
I myself have followed the practice of the smooth bore cannon era and use Sabot's in my Inch gun.
I chuck up a length of 1 inch dowel in my lathe. I put a 1 inch round nose router bit in the tailstock, run the bit in to full diameter and cut to length with my parting tool.
You could cut a reduce section on the back side of the sabot to fit into the case mouth.
One caution however. Load your powder loose in your case, no over powder wad. If you do use an over powder wad be sure to use a filler between wad and bottom of sabot to fill airspace. If you leave a cylindrical airspace between the over powder wad and sabot you set up the parameters for the Vielle effect-ring bulging. A good filler for inch gun is 1 inch foam backer rod.
You could also use 4 bore wads available at Track of the Wolf.
Something else you could do for uniformity is orient you balls so the parting line is always in the same position, say parallel to the case mouth. Don't know that it would make a difference, but it might.