The KM40 was the navalized version of the well-known 12.8 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.
| Designation | 12.8 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 L/4,5: 104.5 lbs. (47.4 kg)
Others: N/A |
| Projectile Types and Weights 1 | AP 43: 62.39 lbs. (28.3 kg)
HE L/4,5: 57.32 lbs. (26.0 kg) |
| Bursting Charge 2 | AP 43: 1.08 lbs. (0.490 kg) TNT
HE L/4,5: 8.16 lbs. (3.70 kg) TNT |
| 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 |
| Elevation | Distance |
|---|---|
| 45 degrees | 22,530 yards (20,600 m) |
| 70 degrees | 48,560 feet (14,800 m) |
"Naval Weapons of World War Two" by John Campbell
"Anti-Aircraft Guns" by P. Chamberlain & T. Gander
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"Übersicht über die für die Marinegeschütze und deren Abk K zu verwendende Munition und ihre Einzelteile einschließlich Salut-
und Manöverladungen" M.Dv. Nr. 198 by Oberkommando der Kriegsmarine
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Special help from Daniel Muir
28 April 2004 - Benchmark
19 May 2012 - Updated to latest template
30 January 2019 - Converted to HTML 5 format
22 August 2024 - Added projectile information