The M30 106.7 mm (4.2 inch, or "Four-deuce") heavy mortar is an American rifled,

muzzle-loading A muzzleloader is any firearm into which the projectile and the propellant charge is loaded from the muzzle of the gun (i.e., from the forward, open end of the gun's barrel). This is distinct from the modern (higher tech and harder to make) desig ...

, high-angle-of-fire

weapon A weapon, arm or armament is any implement or device that can be used to deter, threaten, inflict physical damage, harm, or kill. Weapons are used to increase the efficacy and efficiency of activities such as hunting, crime, law enforcement, ...

used for long-range indirect fire support to

infantry Infantry is a military specialization which engages in ground combat on foot. Infantry generally consists of light infantry, mountain infantry, motorized infantry & mechanized infantry, airborne infantry, air assault infantry, and mar ...

units.

Design

The M30 system weighs including the complete mortar with a welded steel rotator, M24A1 base plate and M53 sight. A point of interest in the design of this mortar is the rifled barrel. A rifled barrel requires the round to be a very tight fit to the bore in order for the rifling to engage the round and impart rotation to it. But, in a

mortar, the round has to be loose enough in the bore to drop in from the front. In order to have it both ways, these rounds have an expandable ring at the base, which expands into the rifling under the pressure of the firing charge that propels the round. Additionally, imparting a spin to a round causes it to drift away from the direction of fire during flight and the longer the flight (greater range to target), the farther the drift, so the computation for setting the direction for firing at a specific target has to account for this drift. American rounds are designed to be drop-safe and bore-safe. As such, the fuzes in the rounds for this rifled mortar only armed once the round had spun a certain number of times i.e. the round was not armed until it had exited the barrel spinning, and had consequently traveled a safe distance from the gun emplacement.

Types of rounds

* HE M329A1—max range , weight * HE M329A2—max range , weight * WP M328A1—max range * ILLUM M325A2—max range , 90-second burn time * ILLUM M335A2—max range , 70-second burn time ILLUM is illumination, a parachute flare round with fixed timed detonation. Deployment height above ground is determined by gun elevation angle and propelling charge. HE (high-explosive) and WP (

white phosphorus Elemental phosphorus can exist in several allotropes, the most common of which are white and red solids. Solid violet and black allotropes are also known. Gaseous phosphorus exists as diphosphorus and atomic phosphorus. White phosphorus White ...

) rounds could be fitted with various fuses before firing, including a

proximity fuse A proximity fuze (or fuse) is a fuze that detonates an explosive device automatically when the distance to the target becomes smaller than a predetermined value. Proximity fuzes are designed for targets such as planes, missiles, ships at sea, an ...

set for detonation at about 30 feet above ground to maximize the affected target area and to spray shrapnel down into foxholes. There was also a sub-caliber training device that utilized blank 20-gauge shotgun shells to propel an inert training round a few hundred meters. This training was for the gunnery skill of laying (in a sense, aiming) the guns. This device had originally been developed during WWII for the M2 mortar.

History

The M30 entered service with the

U.S. Army The United States Army (USA) is the land service branch of the United States Armed Forces. It is one of the eight U.S. uniformed services, and is designated as the Army of the United States in the U.S. Constitution.Article II, section 2, cl ...

in 1951, replacing the previous M2 106.7 mm mortar. It was adopted due to the extended range and lethality in comparison to the previous M2 mortar, although the M30, at , was significantly heavier than the M2. Due to this heavy weight, the mortar was most often mounted in a tracked mortar carrier of the M113 family, designated as the M106 mortar carrier. This vehicle mounted mortar was crewed by five people: the track commander (mortar sergeant/gun commander), gunner, assistant gunner, ammunition bearer and vehicle driver. Ground mounting of the mortar was time consuming and strenuous as a hole had to be dug for the base plate of the mortar to rest in, sandbags had to filled and placed around the base plate to stabilize it and to protect the exposed ammunition. Also, this decreased the accuracy of the weapon as the recoil from firing caused the base plate to shift in the ground. This movement also made the crew have to "lay" the gun back on the aiming stakes more often, causing a temporary lack of fire while the weapon was repositioned and re-sighted back to its original reference point. During the

Vietnam War The Vietnam War (also known by other names) was a conflict in Vietnam, Laos, and Cambodia from 1 November 1955 to the fall of Saigon on 30 April 1975. It was the second of the Indochina Wars and was officially fought between North Vietnam a ...

, both the

US Marine Corps The United States Marine Corps (USMC), also referred to as the United States Marines, is the maritime land force service branch of the United States Armed Forces responsible for conducting expeditionary and amphibious operations through com ...

and the

US Army The United States Army (USA) is the land service branch of the United States Armed Forces. It is one of the eight U.S. uniformed services, and is designated as the Army of the United States in the U.S. Constitution.Article II, section 2, cla ...

deployed the M30 mortar. The USMC mounted the M30 mortar on the carriage of the

M116 howitzer The 75mm Pack Howitzer M1 (redesignated the M116 in 1962) was a pack howitzer artillery piece used by the United States. Designed to be moved across difficult terrain, gun and carriage could be broken down into several pieces to be carried by p ...

, this assembly being known as the M98 Howtar. The

Saudi Arabian Army Royal Saudi Land Forces ( ar, القُوَّاتُ البَرِّيَّةُ المَلَكِيَّة السُّعُودِيَّة, Al-Quwwat al-Bariyah al-Malakiyah as-Su'udiyah) is the land warfare service branch of the Armed Forces of Saudi Ara ...

deployed the M30 in 1990-1991 during the

Gulf War The Gulf War was a 1990–1991 armed campaign waged by a Coalition of the Gulf War, 35-country military coalition in response to the Iraqi invasion of Kuwait. Spearheaded by the United States, the coalition's efforts against Ba'athist Iraq, ...

. The M30 was also used in Bosnia during Operation Joint Endeavour in 1996.

Users

* * * * * * * *: less than 20 * : 4 * * *: 620 (including 231 on vehicles) in service in the

Hellenic Army The Hellenic Army ( el, Ελληνικός Στρατός, Ellinikós Stratós, sometimes abbreviated as ΕΣ), formed in 1828, is the land force of Greece. The term ''Hellenic'' is the endogenous synonym for ''Greek''. The Hellenic Army is th ...

* : 12 from Israel, in store * * : 50 * * * * : 6 * * * * * * * * : 20 * *: 40 in the

Philippine Army The Philippine Army (PA) (Tagalog: ''Hukbong Katihan ng Pilipinas''; in literal English: ''Army of the Ground of the Philippines''; in literal Spanish: ''Ejército de la Tierra de la Filipinas'') is the main, oldest and largest branch of the ...

and some in the

Philippine Marine Corps The Philippine Marine Corps (PMC) ( fil, Hukbong Kawal Pandagat ng Pilipinas) is the marine corps of the Philippines, a naval infantry force under the command of the Philippine Navy. The PMC conducts amphibious, expeditionary, and special op ...

*: 30 (including 20 on vehicles) in service *: ~150 in service with the

, some used on vehicles * * *: 1,264 *:

and

US National Guard The National Guard is a state-based military force that becomes part of the reserve components of the United States Army and the United States Air Force when activated for federal missions. * *

References

External links