The reason they’re almost impossible to find is that they’re largely irrelevant. Muzzleloaders are short-range firearms, so most people just sight-in at 100 yards and go hunting, since they don’t plan to shoot much beyond 100 yards anyway. Muzzleloaders are, after all, supposedly “primitive” rifles. If you’ve got some scoped, plastic-and-stainless muzzleloader you’re trying to turn into a centerfire by shooting saboted bullets, try it at 150 yards to see where it shoots. You’d have to do that anyway, even if ballistics charts existed, because charts are only theoretical. Responsible hunters test their rifles (whether muzzloader or centerfire) at any distance they plan to shoot. If you want to shoot beyond 150 yards, a better solution would be to use something called a .30/06, which was invented almost a century ago for just that purpose. You won’t be able to use one during a muzzleloader season, but some people believe muzzleloading rifles should represent some sort of handicap and not be able to run side-by-side with scoped centerfires.