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M30 (4.2-inch / Four-Deuce)

106.7mm Heavy Mortar System

M30 (4.2-inch / Four-Deuce)

106.7mm Heavy Mortar System


Developed by the U.S. Chemical Warfare Service, the M30 heavy mortar system was introduced in 1951 and still sees service today.
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ORIGIN: United States
YEAR: 1951
MANUFACTURER(S): United States Chemical Warfare Service - USA
OPERATORS: Brazil; Greece; Philippines; Saudi Arabia; North Vietnam; South Vietnam; United States; Vietnam

Common measurements, and their respective conversions, are shown when possible. Calibers listed may be model/chambering dependent.
ACTION: Pin Actuated; Manual Operation
CALIBER(S): 106.7mm
LENGTH (OVERALL): 1,525 millimeters (60.04 inches)
LENGTH (BARREL): 1,525 millimeters (60.04 inches)
WEIGHT (UNLOADED): 672.41 pounds (305.00 kilograms)
SIGHTS: Integrated Optics Set.
RATE-OF-FIRE: 18 rounds-per-minute
RANGE (EFFECTIVE): 2,525 feet (770 meters; 842 yards)

Series Model Variants
• M30 - Base Series Designation


Detailing the development and operational history of the M30 (4.2-inch / Four-Deuce) 106.7mm Heavy Mortar System.  Entry last updated on 8/24/2017. Authored by Staff Writer. Content ©
The mortar weapon system has been around for decades and has proven its worth, time and again, in the field of in-direct fire. Such weapons proved critical in the offensives dotting both World Wars and continue to be showcased in every major army service today. The challenge to warplanners has always been in providing suitable and portable mortar systems for use at the infantry level and this eventually dictated design and inherent limitations.

Throughout World War 2, the United States Army replied on the M2 4.2 inch heavy mortar for heavy suppression of enemy positions. This system was in use by the service from 1943 until 1974. In the 1950s, thought turned to a newer, more modern weapon whose design was based on the practical experience garnered by crews in the Second World War. This entry of 1951 then became the M30 4.2".

Both systems were of 106.7mm caliber (107mm) but the newer model exhibited increased range and better accuracy. The end-product became a 670-pound system with a length of five feet. A crew of five was typical for proper function and, due to the weapon's size and weight, it was traditionally mounted on - and fired from - a carrier vehicle such as the M113 Armored Personnel Carrier (APC).

Design of the M30 fell to the United States Chemical Warfare Service. Both the earlier M2 and newer M30 were known by the nickname of "Four-Deuce" due to its caliber in inches (4.2). The M30 remains in service with a handful of operators today including Brazil, Greece, the Philippines and Saudi Arabia.

The M30's design arrangement is typical of mortar weapons in that the configuration relies on a basic launch tube, a baseplate, support structure and integral sighting device. It fires three distinct projectiles in five forms including two HE (High-Explosive) types (HE M329A1 and HE M329A2), a WP (White Phosphorous) round (WP M328A1) and two Illumination rounds (ILLUM M325A2 and ILLUM M335A2) out to ranges of 5,500 meters or more. Rate-of-fire is up to eighteen rounds-per-minute or three rounds sustained. Absolute maximum range is out to 6,850 meters. Controls along the support arm of the mounting hardware allow the operators to affect the weapon's elevation and traversal functions.

The M30 series saw combat service in the Korean War (1950-1953) and the Vietnam War (1955-1975).