c.w.bullet
Iv.e done this once when i was learning how to load a rifled musket. Looks like who ever ramed it down real hard, if you had a ramrod you would see it fits perfectly over the cone on the top of bullet.Some times the soldier loading his rifle was very nervous( wonder why) ad would ram the mini down the bore super hard. worm would leave a hole on the top of the minie.you had two tools for this. one was a jag , looked like a coiled spring, used for cleaning patches. 2nd was a screw that was used as a ball puller. But yes you have a real .58 minie bullet. Nice find.