I think it’s a rifled slug but with that patina it’s got to be old right? The modern ones online are dark gray not bright white like old bullets get over time.Maybe hollow point shotgun slug...?
I have found white patina on .22lr rounds that I dropped in the back pasture less than ten years ago, as an anecdotal reference point.I think it’s a rifled slug but with that patina it’s got to be old right? The modern ones online are dark gray not bright white like old bullets get over time.