This weapon was manufactured by Rheinmetal-Borsig and was essentially a longer barrel version of the Army 3.7 cm Flak 36. This new gun was a great improvement over the older 3.7 cm/83 SK C/30 and had a much higher rate of fire. Recoil operated, air cooled and used five-round ammunition strips.

These were the first German light anti-aircraft guns to have shields, a surprising shortcoming of earlier weapons.

The design of this gun emphasized ease of manufacturing. Constructed of a monobloc barrel which was connected to the breech ring by a bayonet joint to allow easy replacement. Used a vertical sliding breech block, hydraulic brake and spring recuperator.

Gun Characteristics

Designation 3.7 cm/69 (1.5") Flak M42
Ship Class Used On U-boats, Emden, destroyers and minesweepers
Date Of Design 1942
Date In Service 1944
Gun Weight 240 lbs. (109 kg)
Gun Length oa N/A
Barrel Length 100.79 in (2.560 m)
Rifling Length 90.1 in (2.289 m)
Grooves (20) 0.0217 in deep x 0.150 in (0.55 mm x 3.81 mm)
Lands 0.087 in (2.2 mm)
Twist Uniform RH 1 in 25.6
Chamber Volume 16.5 in3 (0.270 dm3)
Rate Of Fire 250 rounds per minute cyclic


Type Fixed
Weight of Complete Round HE tracer: 3.0 lbs. (1.36 kg)
HE incendiary: 3.02 lbs. (1.37 kg)
AP tracer: 3.31 lbs. (1.50 kg)
Projectile Types and Weights HE tracer: 1.40 lbs. (0.635 kg)
HE incendiary: 1.42 lbs. (0.640 kg)
AP tracer: 1.54 lbs. (0.700 kg)
Bursting Charge HE tracer: N/A
HE incendiary: N/A
AP tracer: N/A (probably solid bullet)
Projectile Length N/A
HE incendiary, complete round: 14 in (355 mm)
Propellant Charge 0.386 lbs. (0.175 kg) RPC/38N
Cartridge: 1.0 lbs. (0.51 kg)
Muzzle Velocity HE tracer: 2,838 fps (865 mps)
HE incendiary: 2,772 fps (845 mps)
AP tracer: 2,674 fps (815 mps)
Working Pressure 18.7 tons/in2 (2,950 kg/cm2)
Approximate Barrel Life 7,000 rounds
Ammunition stowage per gun 2,000 rounds 1

The sources below differ in many areas for this weapon. The figures given in this table come mainly from "Naval Weapons of Word War Two."

  • ^Minesweeper outfits were half AP tracer and half HE tracer. Outfits on other ships was intended to be two-thirds HE incendiary and one-third AP tracer.


Range with 1.34 lbs. (0.61 kg) HE Incendiary
Elevation Distance
45 degrees 7,000 yards (6,400 m)
AA Ceiling @ 85 degrees 17,750 feet (4,800 m)

Mount / Turret Data

Designation Single Mount: N/A
Twin Mount: 3.7 cm Flak LM/42
Weight Single: N/A
Twin: 1.33 tons (1.35 mt)
Elevation -10 / +90 degrees
Elevation Rate Manual operation, only
Train 360 degrees
Train Rate Manual operation, only
Gun recoil N/A


Data from:

  • "Naval Weapons of World War Two" by John Campbell
  • "German Warships 1815-1945" by Erich Gröner
  • "Das Buch der Deutschen Kriegsmarine" by Jak P. Mallmann Showell
  • "German Destroyers of World War Two (2nd Edition)" and "German Cruisers of World War Two" both by M.J. Whitley

Special help by Dave Krakow

Page History

15 May 2006
20 May 2012
Updated to latest template
23 March 2013
Redid photograph of Z39