Hitech's goal is to model the flight characteristics of the bullets as realistically as possible, except that when their energy is spent they disappear instead of tracking them all the way to the ground.  So real life ranges should be pretty close to game ranges.
This is what I got from 
http://www.navweaps.com/Weapons/WNUS_4cm-56_mk12.phpElevation                   With HE Mark 2 Shell   With AP M81A1 Shell
Range @ 10 degrees   6,844 yards (6,258 m)   6,466 yards (5,913 m)
Range @ 15 degrees   8,227 yards (7,523 m)   7,580 yards (6,931 m)
Range @ 20 degrees   9,295 yards (8,499 m)   8,389 yards (7,671 m)
Range @ 25 degrees   10,103 yards (9,238 m)   8,959 yards (8,192 m)
Range @ 30 degrees   10,691 yards (9,776 m)   9,358 yards (8,557 m)
Range @ 35 degrees   11,057 yards (10,111 m)   9,568 yards (8,749 m)
Range @ 40 degrees   11,208 yards (10,249 m)   9,618 yards (8,795 m)
Range @ 45 degrees   11,133 yards (10,180 m)   9,492 yards (8,679 m)
AA Ceiling   22,299 feet (6,797 m)   ---