Italy / Switzerland
35 mm/90 KDC (Gun)
GDM-A and GDM-C (Mountings)
Updated 19 November 2008
The KD gun series were originally developed for army air defense and is considered one of the most successful post-World War II anti-aircraft defense weapons.  Oerlikon and OTO-Melara have both produced naval versions.

Each gun has a device for measuring muzzle velocity and this data is fed back to the gun-laying computer.  Each gun has two belt feeds and can be switched between belts in about two seconds.  Muzzle velocity is electronically measured and fed back into the fire control computer.

Ammunition for these weapons is produced by at least fourteen countries, including the PRC.
WNIT_35mm-90_KDC_GDM-A_pic.jpg

35 mm/90 KDC gun in Oerlikon GDM-A Twin Mounting
Photograph copyrighted by Oerlikon Contraves AG
WNIT_35mm-90_KDC_GDM-A_color_pic.jpg

35 mm/90 KDC gun in Oerlikon GDM-A Twin Mounting
Photograph copyrighted by Oerlikon Contraves AG
WNIT_35mm-90_KDC_GDM-C_pic.jpg

35 mm/90 KDC gun in OTO-Melara GDM-C Twin Mounting
Photograph copyrighted by Oerlikon Contraves AG
WNIT_35mm-90_KDC_Assad_pic.jpg

35 mm/90 on Libyan missile corvette Assad in July 1983
U.S. Navy Photograph No. DN-ST-83-09894
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35 mm KDC Gun
Photograph copyrighted by Oerlikon Contraves AG
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Gun Characteristics
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Designation Gun:  Oerlikon 35 mm/90 KDC
Ship Class Used On Iran:  Mark 7 frigate
Greece:  Missile Boats
Japan:  Patrol Boats
Date Of Design about 1965
Date In Service 1972
Gun Weight N/A
Gun Length oa 186.6 in (4.740 m)
Bore Length Including muzzle break:  146.1 in (3.710 m)
Without muzzle break:  138.2 in (3.510 m)
Rifling Length N/A
Grooves N/A
Lands N/A
Twist N/A
Chamber Volume N/A
Rate Of Fire 550 rounds per minute per gun cyclic
Note:  Weapons are completely interchangeable and can be assembled for left or right feed.
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Ammunition
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Type Fixed
Weight of Complete Round HE-I:  3.48 lbs. (1.58 kg)
SAPHEI-T:  3.48 lbs. (1.58 kg)
APFSDS-T:  3.20 lbs. (1.45 kg)
FAPDS: 3.17 lbs. (1.44 kg)
AHEAD:  3.90 lbs. (1.77 kg)
Projectile Types and Weights HE-I:  1.21 lbs. (0.550 kg)
SAPHEI-T:  1.21 lbs. (0.550 kg)
APFSDS-T:  0.86 lbs. (0.388 kg)
FAPDS:  0.83 lbs. (0.375 kg)
AHEAD:  1.65 lbs. (0.750 kg)
Bursting Charge HE-I:  0.24 lbs. (112 gm)
SAPHEI-T:  0.05 lbs. (22 gm)
APFSDS-T:  N/A (solid sub-caliber penetrator)
FAPDS:  N/A (solid sub-caliber penetrator)
AHEAD:  N/A (uses 152 3.3 gm sub-projectiles)
Projectile Length Projectile
   N/A

Complete Round
   HE-I and SAPHEI-T:  (38.7 cm)
   APFSDS-T and FAPDS:  (34.0 cm)
Propellant Charge 0.73 lbs. (0.33 kg) NC 01 T 35 (single based)
Cartridge 35 mm x 288
Muzzle Velocity HE-I:  3,850 fps (1,175 mps)
SAPHEI-T:  3,850 fps (1,175 mps)
APDS-T:  4,724 fps (1,440 mps)
FAPDS:  4,724 fps (1,440 mps)
Working Pressure 24.6 tons / in2 (3,875  kg / cm2)
Approximate Barrel Life N/A
Ammunition stowage per gun See Notes
Notes:

1) GDM-A mounting has 112 ready rounds plus 224 rounds within the mounting per gun.

2) GDM-C mounting has 20 ready rounds in gun house and 400 rounds in below deck magazine per gun.
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Range
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Elevation With 1.21 lbs. (0.55 kg) HE-I Shell
Effective Range - Surface 8,700 yards (8,000 m)
Effective Range - AA 5,500 yards (5,000 m)
Notes:

1) The above figures are for full radar control.  Optical control or local control greatly reduces these figures.

2) Flight time for HE-I at a muzzle velocity of 3,850 fps (1,175 mps):
   0.96 seconds for 1,090 yards (1,000 m)
   2.18 seconds for 2,190 yards (2,000 m)
   3.80 seconds for 3,280 yards (3,000 m)
   6.06 seconds for 4,370 yards (4,000 m)

3) Flight time for APDS-T at a muzzle velocity of 4,724 fps (1,440 mps):
   0.73 seconds for 1,090 yards (1,000 m)
   1.57 seconds for 2,190 yards (2,000 m)
   2.38 seconds for 3,280 yards (3,000 m)
   3.34 seconds for 4,370 yards (4,000 m)
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Mount / Turret Data
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Designation Single Mount
   N/A

Twin Mount
   GDM-A
   GDM-C
Weight  GDM-A:  10,500 lbs. (4,763 kg) without ammunition

GDM-C:  17,637 lbs. (8,000 kg) including ammunition
Elevation GDM-A:  -15 / +85 degrees
GDM-C:  -15 / +85 degrees
Elevation Rate GDM-A
   70 degrees per second maximum
   Acceleration 130 degrees per second

GDM-C
   70 degrees per second maximum
   Acceleration 130 degrees per second
Train 360 degrees
Train Rate GDM-A
   120 degrees per second maximum
   Acceleration 160 degrees per second

GDM-C
   115 degrees per second maximum
   Acceleration 130 degrees per second
Gun recoil N/A
Notes:

1) The GDM-A is the original Oerlikon design.

2) The GDM-C version was developed as a joint project between Oerlikon and OTO-Melara.  Requires two loaders plus a gunlayer if not in remote control mode. A US Navy Foreign Ordnance Review Team concluded about 1971 that this version was better suited to US requirements, but none were purchased.

3) The GDM-C mount is gyrostabilized and requires a power source of 43 KW.

4) The single gun version used by the Japanese was manually controlled and had a sidecar for the gunner.
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Data from
"Jane's Pocket Book 9:  Naval Armament" edited by Denis Archer
"The Naval Institute Guide to World Naval Weapon Systems 1991/92" by Norman Friedman
"Jane's Ammunition Handbook:  Ninth Edition 2000-2001" edited by Terry J. Gander and Charles Q. Cutshaw
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"Defense & Armament Heracles International" Issue #72, April 1988
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 Oerlikon Contraves AG Press Releases
OTO-Melara Press Releases
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Special help by Matthew Rodchenko