The listing, Genuine Civil War Lead Minie Ball Musket Rifle Bullet Removed from Rifle with Worm Screw Tool has ended.
The Minié ball, or Minie ball, is a type of muzzle-loading spin-stabilized rifle bullet named after its co-developer, Claude-Étienne Minié, inventor of the Minié rifle. It came to prominence in the Crimean War and American Civil War.
The Minié ball was a conical-cylindrical soft lead bullet, slightly smaller than the intended firearm barrel's bore, with (originally) four exterior grease-filled grooves and a conical hollow in its base. The bullet was designed by Minié with a small iron plug and a lead skirting. Its intended purpose was to expand under the pressure and obturate the barrel and increase muzzle velocity.
http://www.trackofthewolf.com/list/item.aspx/129/1
This link shows modern minie balls have the tip cut off from the casting sprue being removed and are a shiny lead color. Authentic vintage Civil War Minie balls are conical unless a tool has been used to remove the bullet that jammed in the rifle. Then it has a screwed in hole left in the cone top like this one. When lead oxidizes it turns this chalky yellow color and proves a piece is vintage. The oxidized lead cannot be mimicked.
This one looks to be a .54 or .58 caliber from charts with pix I've studied. Likely a Union Minie ball. It has been unfired as it jammed in the rifle. It is not the star type with star inside bottom or a cleaner bullet version. Was discarded on the field of battle by the soldier due to malformation/jamming in rifle. Needed to be removed with worm screw tool.
This one comes from a collection of a relic hunter's estate and he dated it April or APR 4/79 when he found it.
My photos of actual bullet are first 5, then a chart on specs with a diagram. Then composite photos of real minie balls of various calibers and types.
Your chance to own a piece of United States History!