A draped cloth-tape can be ambiguous indicator, so I can't say for certain from viewing the photo ...but it appears to be a 13-inch mortarshell. (Though it might be an 11-inch cannonball ...or a 12-incher if it's Colonial-era or 1812.)
By the way, there is no record of any solid-shots in the 13-inch caliber - which is good news for the digging crew. Being hollow, a 13"-caliber shell weighs "only" around 210 pounds. You're going to discover what it's like to get personally acquainted with the term "dead weight." ;-) Hopefully, unlike me, you'll do so without a hernia-surgery result.
Tom Dickey taught me a good way to get such a projectile out of the ground. Bring a long iron bar (at least as thick as a crowbar) and two 5-foot lengths of seat-belt-type nylon strap. Get the straps crossways under the center of the projectile, tie the strap-ends over the bar, and have two guys lift the ends of the bar.
I gotta ask, how far are you from your car? Back in 1976 at Port Hudson LA, I bought a digging-buddy a Prime Rib dinner in exchange for carrying my 10-inch mortarball the half-mile back to our car.
Here's how I got mine out of the hole (which was a week *before* Tom gave me his advice "for the next one you find"):
That 10-inch mortarball was 3 & 1/2 feet deep - so I couldn't just reach into the hole and pick it up. Therefore I dug the hole out enough to cut "steps" into one side of it. I hefted the ball out, one "step" at a time. After that much digging, followed by the hefting, I made the Prime Rib offer to my digging-buddy. It cost me 1/4 of what that mortarball was worth back in those days, but I've always been glad he took the deal. : )
Pardon my curiosity, but you didn't say anything about what battle-connection your cannonball has. Please do, if possible. I see you're in Massachusettes. Does that mean the ball is too?
Regards,
TheCannonballGuy [Pete George]