Muzzle loading artillery does not use a patched ball. The ball can be attached to a sabot, or it might have a wad behind it, but typically is just the bare ball. The bore is swabbed between shots, to kill any remaining embers.
I will leave further discussion to members with much more recent experience.
Cannons were typically smooth bore, and designated in size by the weight of the ball they fired. Rifled guns were designated by bore size, and usually (but not always) shot a projectile of a shape other than round.
As was said before, cannons also typically did not shoot a patched ball, and as was said, could be shot with a wad over the powder charge. The ball was definitely smaller than the bore size, because it was typically made from iron, and that stuff is pretty non-malleable. As you might guess, the "round" cannon balls of the day were not machined perfect.
If an iron ball got stuck on its' way out the bore the rest of the gun would blow up. Not a good thing, so they were made with a fair amount of windage between the bore size and ball size to allow for such things.
To me, the words "precision" and "cannon shooting" really don't go together, particularly when it comes to smooth guns, and, particularly with a piece that is essentially designed as an area denial weapon!
While you brought up some excellent points, I would like to add the WBTS 12 Pounder Bronze Smoothbore Napoleon Guns were used effectively out to 1,000 yards with solid shot and especially exploding shells.
I also witnessed some remarkable accuracy with an Original 3 Inch, WBTS "Ordnance Rifle" at the World Championships of the International Muzzle Loading Committee at Quantico, VA in 1980. This by a Federal Reenactment Gun Crew who regularly shot competitively in NSSA Cannon Competition.
They set up a frame and hung a suspended watermelon from it at 100 yards. The Gun Captain explained that they could not destroy the watermelon with one shot as the round would only punch a hole in it. So on the first shot, they had to just "nick" it. After the smoke cleared from the first shot, it looked like someone had taken a big bite out of the side of the watermelon. They took a rather long time to align the second shot as the Target Boards downrange behind the watermelon was interfering with their sight alignment. The Gun Captain apologized and noted he wasn't sure if the next shot would hit what was left of the watermelon. Well, after the second shot, burst watermelon was sprayed all over the area.
I may not remember correctly, but I think those original Ordnance Rifles had a maximum range of 2 1/2 to 3 miles? Granted most times in battle there was not that much open space, but some were used very effectively at 1 1/2 miles during the WBTS.
I guess accuracy means different things at different ranges, as it comes down to what the repeatable MOA accuracy is, which is a function of the target size, range, and time of flight for the projectile, and other extraneous forces, like earth rotation, wind and gravity rather than just one element. If you're just aiming to try and hit planet Earth (from planet Earth) SOMEWHERE that's doesn't take much precision. If you're trying to hit a vegetable with a cannon from 100 yards, or, planet Earth from Mars, then your aim has got to be better.
Nikke, if I was shooting a 37mm cannon (1.45" bore), I would either try casting a lead ball with maybe 1.5mm space either side (34mm) or find a similar ball bearing.
Lead would make a good projectile because it is both uniform and soft - no chance of it getting stuck in the bore and making it a pipe bomb. Similarly, a shiny smooth ball bearing is not likely to catch in the bore the way a rough cast iron ball might. You'd have to use a much smaller cast iron ball to be safe.
Back when I was a teenager I had a mentor in all things black powder, one Henry Palmer, who had a home made six pounder cannon. We neatly cut down a dead elm tree in his back yard with beer cans filled with concrete. It was a 10" tree out at about 50 yards. Three shots: one hole, binocular hole, tree over. Henry made sure the cannon went back in the same exact position after each shot, and then gave the tailpiece a kick.
You need windage on an iron ball just it case it turns on the way out and jams. No need on a lead ball, you either make it a good fit or leave room for a patch.
After shooting ball from my wall gun and reading about shooting the Rabonette (1.5") in the English Civil War, I am fairly convinced that bore size has an awful lot to do with shooting straight, no rifling required.
Hi i am new here so excuse my bad spelling.
im from Sweden and English is not my usual language
The right size of ball is 36.075mm 39/40 of the bore to your gun.
Here is a picture of my homemade mod 1841 in 2/3 scale
I use a patch in my 1.25 in bore cannon, it shoots a 6oz lead ball that is 1.22in dia, it will hit the target at 100 yds. I do not use a patch ball in my 2 1.5in bore cannons as the ball is a cast to size, again I am using lead balls. In my 5.8 in bore mortar the balls are a loose fit and are die cast hollow and filled with sand, they weight 17 pounds.
I use a patch with my 3" smoothbore cannon. I use a fairly loose patch of cotton t-shirt material so that the ball slides down the bore easily. But it takes most of the windage out and gives me accuracy to within a 10" bullseye at about 250 yards. Its not a rifle. But with a target sheet 2/3 the size of a man it is enjoyable to regularly hit something. My gun is a replica 3lb British Light Infantry gun with a 1760's period carriage https://1drv.ms/v/s!AjDP6RJxCb0PwQ9BItwXa-R4GZMb.