The KM40 was the navalized version of the well-known 12.7 cm Flakzwilling 40 which was an AAA gun mounted on Flak Towers in major cities. These guns were always used in twin mountings and are "mirror" designs, that is, the left gun loads from the left side and the right gun loads from the right side. Late in the war the design was modified to produce a three-piece barrel so that scarce alloy steel could be saved by changing out only the most worn section.

The KM40 was never mounted on a ship although design work for a twin turret with full RPC was in progress when the war ended. There were a number of naval batteries with the KM40 at major ports including one near Kiel with an armored enclosure. All guns fired fixed ammunition.

All German 12.7 cm guns had an actual bore diameter of 12.8 cm (5.04 in).

Gun Characteristics

Designation 12.7 cm/61 (5") KM40 (Flakzwilling 40)
Ship Class Used On N/A
Date Of Design 1940
Date In Service Not mounted afloat
As flak batteries: 1942
Gun Weight about 10,580 lbs. (4,800 kg)
Gun Length oa 308.5 in (7.835 m)
Bore Length 294.9 in (7.490 m)
Rifling Length 255.0 in (6.478 m)
Grooves (40) 0.067 in deep x 0.258 in (1.7 mm x 6.55 mm)
Lands 0.138 in (3.5 mm)
Twist Increasing RH 1 in 53.9 to 1 in 32.6
Chamber Volume 877 in3 (14.37 dm3)
Rate Of Fire 15 - 18 rounds per minute


Type Fixed
Weight of Complete Round HE: 104.5 lbs. (47.4 kg)
Projectile Types and Weights HE: 57.32 lbs. (26.0 kg)
Bursting Charge N/A
Projectile Length N/A - complete round 58.6 in (148.77 cm)
Propellant Charge 22.3 lbs. (10.1 kg) RPC/38

Cartridge: 47.18 lbs. (17.4 kg)
Muzzle Velocity HE: 2,953 fps (900 mps)
Working Pressure 18.7 tons/in2 (2,950 kg/cm2)
Approximate Barrel Life about 1,500 rounds
Ammunition stowage per gun N/A

Projectiles were 10/2crh.


Range with 57.32 lbs. (26.0 kg) HE
Elevation Distance
45 degrees 22,530 yards (20,600 m)
70 degrees 48,560 feet (14,800 m)

Mount / Turret Data

Designation Twin Mount: LM40 1
Weight N/A
Elevation -10 / +80 degrees
Elevation Rate N/A
Train -170 / +170 degrees
Train Rate N/A
Gun recoil N/A
  • ^The LM40 was the navalized mounting.


"Naval Weapons of World War Two" by John Campbell
"Anti-Aircraft Guns" by P. Chamberlain & T. Gander
Special help from Daniel Muir

Page History

28 April 2004 - Benchmark
19 May 2012 - Updated to latest template
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