Unfortunately I have to tell you that the object is definitely not an artillery shell fragment. It is a broken piece of a tapered-thickness heavy iron half-ring (or band) which has been seen several times in this forum but has not yet been identified. See the photo below, showing a previous one very similar to yours, on the left in the photo.
Civil war era Schenkl projectiles had several raised ridges running along the axis of their "tail" section, but those ridges are always flat-topped, and are not as "tall" as the ridge seen on your iron object. What you are seeing in the photo of a civil war Hotchkiss shell is a groove, not a ridge.
Also, leg shackles were made of wrought iron, a form of iron which bends instead of shattering. Your broken object is a shattered piece of cast iron, a form of iron which is too brittle to bend, and instead, it shatters when sufficient force is put upon it. That is why explosive shells prior to the end of the 1800s were made of cast iron, and since then are made of cast steel. You WANT them to shatter into multiple fragments.
Thanks for your help and replies. Glad to have you around. I was a fossil hunter for 25 years and recently switched to metal detecting. Relic hunting is what I enjoy and it's a heck of a lot easier than digging and sifting clay layers.
Best,
macrota
(macrota is the species name for Striatolamia macrota - a shark that swam the oceans 50-million-years ago
Macrota wrote:
> Thanks for your help and replies. Glad to have you around.
Macrota, you said you are new to metal-detecting for relics. I'm here to help people like you in the What-Is-It forum because back when I was new to this hobby, a couple of kindhearted "oldtimer" experts gave me a LOT of their time helping me identify my finds. I'm doing for others what those guys did for me. Someday it will be your turn to do that.