Artillery Shell Fragment?

[Mindrot]

I've been working a construction site. The attached pic was found alongside a 3 ringer. The opposite side is concave. 1 cm thick. I can just barely make out a faint rifling mark. Am I crazy?

 

[TheCannonballGuy]

Need to see your iron fragment's other side. Also, please put a ruler right alongside the fragment when you make the photo. But, for the moment, it appears to be a fragment from the lower side of a civil war yankee 3"-caliber Dyer Case-Shot (antipersonnel) artillery shell. I know with certainty that that type has been found at Fredericksburg VA because years ago, I lived in Fredericksburg and me and my relic-digger buddies dug a LOT of civil war shells there, including that specific type of shell.

By the way... what you called a "rifling mark" on that fragment is actually the groove where that shell's zinc/solder cup-sabot fit onto the shell's iron base.