Flintlock Muzzleloader Season: Only single-barrel long-guns .44 caliber or larger, or hanguns .50 caliber or larger with a flintlock ignition system. The firearm must be an original or reproduction of a gun used prior to 1800, with iron, open "V" or notched sights (fiber-optic inserts are permitted). A flintlock ignition system consists of a hammer containing a naturally-occurring stone which is spring-propelled onto an iron or steel frizzen, which, in turn, creates sparks to ignite a gunpowder. Flintlock muzzleloader hunters may use "any single projectile," including sabots, and mini and maxi balls.
Antlerless Muzzleloader Season: Only single-barrel muzzleloading long-guns .44 caliber or larger, or muzzleloading handguns .50 caliber, including in-line and percussion sporting arms. Use of scopes and other lawful sighting devices is permitted. Fiber optic inserts may be used.
That be directly from the PA site there Grouse.
http://www.portal.state.pa.us/portal...=591283&mode=2
Falcon, I only included states that required OVER .40 caliber. Most of the other states not included in the list were .40 caliber minimum while some posted no minimum and a few posted .32-.38
Cayugad, yes this is for the muzzleloader seasons. I would have to delve a lot deeper to find out any restrictions of muzzleloader size requirements during regular firearms seasons. I'm bored but I aint THAT bored.