Thanks for the information. The Stephen Sears book (I listened to it on tape) indicated that the buck and ball were 60 cal. However, you are the second in this thread to point out that they were actually 69 cal. I suspect my source could easily have been a mis-print or a mis-read (I doubt Sears expected people to start measuring barrels on the basis of his book). I did listen to the passage several times to make sure it heard it correctly.
Mike (above) indicated that it should be 58 cal (or your .577) and, being a total novice, I could have easily mismeasured by that amount.
Thank you for your input. Your response is definitely appreciated.