Spartan,
Don't want to be a buzz kill, but Doug R is correct. The Pedersoli is a repro of the Short Land Pattern musket with the 42" barrel. Short land pattern muskets weren't issued to British troops on their way to North America until the 1777-1778 time frame--so it's not 100% correct for a Lexington Green/Concord bridge impression. To be 100% you will need a Long Land Pattern musket with the 46" barrel and for a colonial militiaman impression, most likely an early version with the wooden ramrod. The British troops on April 19th, 1775 carried Long Land Pattern Bess's with steel ramrods and used paper cartridges.
If you plan to shoot PRB, use .715 balls. If you plan to roll your own paper cartridges (which is a heck of a lot of fun, and totally authentic) use .735 balls. The standard British issue ammo during the Rev War used a .690 ball to allow for fouling buildup from prolonged firing but for shooting today, with modern made PB, we don't need that small of a ball.
Anyway, have fun, that's the most important thing. Now that you've renounced the siren song of plastic rifles and smokeless powder, you will never stray from the path of blackpowder righteousness. Welcome to the dark side.