As I recall the Brown Bess shot a ball of about .720" dia while the french musket shot one of .69". Both had a good deal of "Windage" in the bore for easy loading so the Brown Bess went to about .750 as I recall with the Frwnch going about .720". A lot of the French muskets were used in our American Revolution & it became the basis for muskets of this period built here in America as the Commitie of Safety muskets. Some versins of the smoothbore .69 cal muskets were in use as late as the "War Between the States". There have been other instances in history where guns of "Government Caliber" have been declared illegal. This is in fact as I understand it what brought on the development of several non-.45 caliber Nitro Express rounds for use in Africa such as the .465s .470 etc all with similar balistics to the .45s they were replacing.
