The one and only Bill Large .45 caliber round ball barrel I measured was .450 (Lands) and .464 grooves. While Ol' Bill had a great reputation, a lot of his later production did not measure up to it. Apparently as he got older, more and more and more of his works was farmed out to folks that did not share his high standards. Slug the bore for your self to be sure. Drill a hole in an oversize ball, thread a screw into ti that you can remove it with your ramrod and tap it into the barrel. Pull it out and measure carefully. Mr. Large mostly rifles odd number of grooves so measuring is a bit complicated.