US 16 Inch Mark 8 Armor Piercing Naval Gun Shell Specifications:

US 16 inch Mark 8 Naval Shells at other Military Museums in the northeast
Another 16 inch naval shell can be found at the Watervliet Arsenal Museum in Watervliet, NY	Another 16 inch naval shell can be found at the Vermont Military Museum in Essex Junctin, VT	Mark 8 sixteen inch naval shell at the USS New Jersey Naval Museum in Camden, NJ
A Mark 8 16" naval shell at the US Navy Museum in Washington, DC	A 16 inch naval shell fragment at the USS Massachusetts naval museum in Fall River, MA	One more Sixteen inch naval shell at the Buffalo and Erie County Naval and Military Park in Buffalo, NY

Length: 72 inches
Diameter: 16 inches
Weight: 2,700 lbs
Range: 45,000 Yards
Concrete Penetration: 30 feet reinforced concrete
Armor Penetration: 30" of side armor at 5,000 yds, 14" of deck armor at 42,000 yds
Propellant Charge: 655lbs
Bursting Charget: 41 lbs
Muzzle Velocity: 2,500 feet per second
Entered Service: 1939
Unit Cost: $500

This is the cutting bit that would be forced through the 16 inch naval gun barrel to cut the rifleing grooves. The bits are adjustable for depth. I do not know how many passes it would have to make to cut the grooves to full depth. The next page gives a closer view of the cutting bits.