The furthest I shot a deer with a roundball was 80 yards and an additional 20 feet approximately. I was shooting 80-90 grains of Pyrodex RS and a .530 roundball. The deer was standing broadside to me. I shot and dropped him where he stood. The ball went through him and killed a doe, breaking her spine,standing behind the first one, dropping that one in its tracks as well.
Roundball is a very effective deer projectile. If shot with in 100 yards or closer, there is no reason to fear using a roundball. Place that thing in the rifle place. They get great expansion, and usually a complete pass through. Also they make a mess inside the body cavity.
The deer last year was 52 yards, shot length wise with a .54 caliber roundball. Again, dropped in her tracks. The ball broke her neck, penetrated her brisket, through the heart, out the stomach, and broke a rear lead before heading off into the brush.
With that .58 caliber you want to shoot, you will clean their clock.