Welcome to the forum. Since you're new here, I'll introduce myself. I'm the co-author of the book "Field Artillery Projectiles of the American Civil War." It's a 552-page "photo encyclopedia" on that subject (showing and identifying over 400 civil war artillery projectiles and fuzes).
Sorry to have to tell you, your item is not an artillery projectile of any kind, nor a part of one, from any era of history. It is a piece of 20th-century Industrial machinery. I've seen over a dozen of your item turn up during my 35 years in the civil artillery collecting field. For such an item to be an artillery projectile, it would have to CORRECTLY fit the bore of a known caliber of cannon. None of the dozen or so I've checked (by extra-precise measuring of the item's diameter) do that. All the ones I've seen have been in "non-excavated" condition. Even after more than three decades of diligent research in this subject-area (artillery projectiles), I am not aware of any of this item ever having been excavated from any battlefield. They turn up for sale on Ebay from time to time, being advertized as an artillery projectile, but they absolutely definitely are not.
Regards,
Pete [P.C. George]
