Various similar versions of that iron/steel object have been turning up in this forum for the past 15 years. It is definitely not an artillery projectile, from any era of artillery history. It has a cylindrical (actually, cylindro-conical) body shape, but it is much too short to function properly as a cylindrical artillery projectile. Also, the two shallow flat-bottomed grooves on opposite sides of the object suggest that it was gripped by something which fit into those grooves. And of course, something else fit into the peculiar-shaped indention in your object's base.
Some cannonball/artillery-projectile collectors have nicknamed it a "nipple slug" or "boob slug" due to the short nipple-like concentric circular projections on its top.
I'll attach photos showing several versions which have previously appeared in this forum.