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M30 4.2 inch Chemical Mortar and Manual

Infantry weapons for delivering toxic agents included Livens projectors, grenades, land mines, mortars, rockets and artillery shells. If gas warfare had again broken out, we would have relied mainly on 4.2" chemical mortars of Chemical Warfare Service (CWS) mortar battalions. The 4.2 M30 Chemical mortar, although double the weight of the "portable" 4.2 M2, could also deploy HE shells but with half again the range by using a slower burning propellant, powder disk increments, and better design of the rotating disk on the shell base. The M30 officially replaced the M2 by 1951.

FM-6-135 (html): Adjustment of Artillery Fire (Forward Observer), 7/57

TM9-3305 (html): Principles of Artillery Weapons

FM 23-91:Mortar Gunnery

FM 23-91A:Training Strategy

USMC: 60mm Mortar, 1951

4.2 inch M30 Chemical Mortar

4.2 inch M30 Mortar
History of the 4.2in Chemical Mortar
4.2 inch M2 mortar
60mm mortar

FM 23-91:Mortar Gunnery

General Data

  • The 4.2 inch M30 mortar was a rifled muzzle-loading weapon designed for high-angle fire.

  • Weight (with base plate, base ring, and sighting equipment): 626 lb.
  • Barrel assembly: 158 lb
  • Standard assembly: 58 lb
  • Bridge assembly: 151 lb
  • Rotator assembly: 57 lb
  • Base plate: 108 lb
  • Base ring: 100 lb
  • Sighting equipment: 4 lb

  • Range: 6,500 yards

  • Ammunition:
    • Ammunition for the M30 (T104) was issued as complete rounds, similar to those for the 4.2 inch M2, but had extended length of cartridge container and larger propelling charge. The round consisted of shell, fuze, propelling charge, and ignition cartridge. When fired, the shell was stabilized in flight by rotation transmitted to the shell by means of the pressure plate expanding the rotating disk on the base of the shell thus forcing the disk to engage the rifling in the bore. The shell, which had a deep cavity and suplementary charge, was fitted with a point detonating fuze. The ignition cartridge was housed in the cartridge container extension and was held in place by the striker nut which contained the striker.

Issued to US forces beginning in 1951, the M30 gradually replaced the M2.

The propelling charge consisted of a number of increments of propellent powder in the form of square sheets assembled on the cartridge container. When the round was inserted into the bore and released, it slid to the bottom where the firing pin drove the striker into the primer of the ignition cartridge. Flame from the ignition cartridge flashed through vents in the cartridge container extension to ignite the propellant, thus firing the round.

Because of its size and weight, the weapon was used as Regimental artillery, often vehicle mounted, and was invaluable as support for infantry actions.

Image on right: Heavy Mortar Co., 38th Regiment, U.S. 2d Infantry Division, firing an M30 4.2 Chemical mortar at Communist positions on Hill 773 near Yanggu, Korea, 13 August 1951.

4.2 M30 in action during Korean War

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