Now I'm not sure my maths is right but a 12" 45 calibre gun fires a 850 pound shell with a muzzle velocity of 2,600 feet per secound which equates to 1,772 miles per hour. Zero to 1,772 mph in 45 feet!!
Now a shells speed drops of dramatically with air resistance/range so if we reduce the speed to 1000fps at the end of its flight its still coming in at 681 mph and weighing 850 pounds.
So roughly at 2,000 yeards you will get a flight time of about 60 seconds at 1000fps but as the initial speed was much higher less than half this time of around 30 seconds which seems about right for a range of just over 11 miles.
So if its travelling at 1000fps x 850 = 850,000 foot pounds impact energy which is awsome!!
Geoff