It's ammo alright.... for a slingshot.
https://www.bing.com/images/search?q=slingshot+ammo&FORM=HDRSC2&PC=MOZB
You say you found it in "northeastern" Virginia. It could be a civil war artillery Rifled Canister ammo ball, IF there was some civil war Rifled Artillery (Parrott Rifle, Ordnance Rifle, etc) firing at the spot where you found the ball. If not, then it most probably is a ball-bearing, or perhaps a slingshot ball.
I specified Rifled artillery because all of the Smoothbore cannon (such as a 12-pounder Napoleon Gun) canister ammo balls are larger than the ball you found.