We need super-precise measurement of the lead ball, because with bullets even .02-inch difference in size can be the difference between being a bullet or not a bullet. Please buy or borrow a digital Caliper. If you are (or plan to be) a relic-hunter, a digital Caliper is going to be very well worth its $15 price.
Also, you didn't say what country's troops. That too is very important information. For example, a British "Brown Bess" flintlock musket was .75-caliber, but being a muzzleloading firearm, the ball for it was .71 to .72 in diameter. The French and Spanish's Army's equivalents to the Brown Bess were different calibers from that firearm.
All of that being said... an actual lead musketball's primary characteristic is that an unfired one is as round as a glass marble -- not out-of-round or "lumpy" unless it is a fired one which experience impact-damage. However, because many musketballs were cast in a bulletmold, they often show a moldseam line and/or a casting-spure.