You really need to actually measure the bore diameter, and groove diameter of any new gun. It should be fairly obvious, after reading the posts above, that without knowing the actual diameter of your barrel, to the thousandths of an inch, you are going to waste a lot of money on the wrong size balls and the wrong size patches.
On a large caliber PRB, I do NOT recommend using a patch with a thickness of less than .015, simply because the powder charges normally use will be burning or tearing the patches if you use anything thinner. The material just cannot hold enough lube in it to act as its own firewall!
I you choose to use a .010" patch, then at least used a filler, like corn meal, or an OP wad between the powder and the PRB, to act as a firewall. Most of the Pedersoli barrels come with fairly deep grooves. The purpose of any patch is to fill that groove so that you don't get hot gases blowling by the patch, cutting it, and cutting the soft lead ball. A cut ball is not going to fly true, and accuracy suffers.
If you are new to shooting Black Powder, it is important that you FIND, EXAMINE, and READ every spent patch you fire from your gun as you "break it in". If you don't know how to read patches, I recommend you contact Dutch Schoultz, and buy his Black Powder Rifle Accuracy System. Its only $15.00, but it will teach and show you how to read those patches to find out what is going on inside your barrel.
http://www.blackpowderrifleaccuracy.com/
Perhaps the most common load combination being used by ALL .54 caliber rifle shooters, who use a PRB, is a ball diameter of .530" and a patch of between .015-.018" thick.
Target shooters tend to go to a .535" diameter ball, or even up to a .540" diameter ball, and use a teflon coated patch. They expect to, and do hammer the balls into the barrel at the muzzle using a mallet.
There are some hunters who use even smaller diameter balls- as small as .520" --- With a .020", or .024" thick patch- usually denim-- to make it much easier to load their gun faster for follow up shots.
You do not need heavy loads for " breaking in " any rifle. For your gun, shoot at 25 yds, and use a 50 grain charge of FFg Black Powder. Any polishing of the edges of the lands occurs as the material is pressed against it by the expanded RB when the gun is fired. It doesn't require the ball to be traveling out the barrel at 1800 fps!
While you are breaking in the barrel, use the time to get use to its balance, weight, trigger pull, and sights. 200 rds. through the barrel will be about minimum to break it in, and by that time you should be able to hold the gun much better for good off-hand shooting.
Do find a replacement nipple for that gun ASAP, as the factory nipples are notorious for Not standing up to wear. And, buy a range rod to use to clean and load that gun. Save the stick that came with it for use in the field. Pin those ferrules that come on the factory stick(ramrod) and also check the wood for grain run-out. If it shows run-out, then look for a replacement hickory rod without run-out. Run out is where these sticks break, and injure shooters.
:hatsoff: