From Wikipedia;
Manufacturer Rheinmetall
Specifications
Weight 1,190 kg (2,600 lb) Gun barrel; 3,317 kg (7,310 lb) Gun mount
Length L/44: 5.28 m (17.3 ft); L/55: 6.6 m (22 ft)
Barrel length 44–55 calibers
Caliber 120 mm
Muzzle velocity 1,580 to 1,750 m/s (5,200 to 5,700 ft/s)
Effective range 4,000 meters (4,400 yd) with DM63[1]; 8,000 meters (8,700 yd) with LAHAT[2]
Otobreda 127mm/54C
Calibre: 127 mm (5 inch)
Mass of the system: 37500 kg (without ammunition)
Magazine: 66 (ready to fire in three drums)
Mass of one round: 888 mm length shell: 15.44 kg; 665 mm length shell: 31.75 kg
Elevation: Minimum -15°; Maximum +83°
Range: ±30 km (100 km with guided VOLCANO ammunition)
Turning limitation: ±165° from centerline
Rotation speed: 40°/s (with acceleration of 45°/s2)
Elevation speed: 30°/s (with acceleration of 40°/s2)
Cooling: sea water - fresh water for flushing
Rate of fire: 40 rds/min
This on the old US 5"/38;
Weight Mk 12 Gun Assembly: 3,990 lb (1,810 kg)
& this on the old German 12.7 cm SK C/34 (& seems to be gun-&-mount-only as Type XI U-Boat version weighed 4,625 kg (10,196 lbs));
Weight 3,645 kilograms (8,040 lb)
Unfortunately modern naval guns seem to be calculated as the entire system weight.
:)
Guy