It’s Time for a Direct Fire Breech-Loaded Mortar

By William I. Oberholtzer 

July 2015 

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After a decade of fighting against the United States and its allies, enemies have become increasingly elusive and adaptable.

The United States faces a kaleidoscope of enemy combatants from all over the world having a common thread of unbridled savagery and brutality. Like a cancer, this threat is metastasizing. At present, the armed conflict is centered in the Middle East. Current weapon systems are ideally suited for the European theater, and to a lesser degree, mountainous terrain. Conflict in urban environments does not lend itself to the application of many of these systems.

More often than not, U.S. forces engage in a street-by-street, building-by-building, slugfest with an enemy who is not the least reluctant to position themselves in schools, mosques and among non-combatants. Large crew-served and aerial-delivered munitions tend to obliterate targets and cause significant collateral damage. What is needed are weapons that are effective against brick and masonry without collapsing entire structures. 

A much maligned and underappreciated weapon is the mortar. Military planners and war fighters tend to be enamored with high tech weapon systems and fail to recognize the potential of a tried and true weapon that has been around since before the Civil War. While high tech weapon systems have their place on the battlefield, they are expensive and should be used for high value targets. It is universally accepted that the mortar is an indirect fire weapon.

However, few are aware that the mortar can also be utilized in a direct fire roll. When mounted on a lightweight mortar carrier and firing high explosive fin-stabilized, shallow coned shape charge — high explosive squash head — munitions, the mortar can have a devastating effect on brick and masonry walls. What once provided cover and concealment to the enemy now becomes a lethal, casualty producing, spall. The devastation can be localized without bringing down entire structures.

The secret to employing the mortar in the direct fire mode is the incorporation of a breech block and a pivoting base rather than the traditional base plate. The breach block and pivoting base plate allow the mortar to be used in the traditional muzzle-loaded role using conventional munitions, or in the breech-loaded direct fire mode using specialized munitions.

The concept of using a mortar in, both, an indirect fire and a direct fire mode had its advent during World War II when the Swiss developed a 105mm breech-loaded mortar. The mortar was not adopted by any of the warring powers. Following the war, the weapon system became commercially available and was purchased in limited quantities by Pakistan and Malaysia.

The idea of a breech-loading mortar, although not new, seems to be receiving renewed interest. In 1996 BAE Hagglunds and the Finnish armaments developer Patria developed the advanced mortar system (AMOS) a turret-mounted, breech-loaded, twin-barreled 120mm for mounting on both tracked and wheeled vehicles, as well as coastal patrol vessels. The AMOS is capable of firing a wide range of conventional and specialized ammunition. With both guns sharing a common cradle, the AMOS is capable of multiple rounds simultaneous impact. 

In 2007 BAE tested its non-line-of-sight mortar, NLOS-M, platform. Like the AMOS it fired a wide range of conventional and specialized mortar munitions, and like AMOS, it was capable of multiple rounds simultaneous impact. NLOS-M was to be part of the Army’s Future Combat Systems manned ground vehicle, which was canceled in 2009. It was superseded by the ground combat vehicle program, which suffered the same fate in 2014.

The demise of breech-loaded mortar development should not lead one to believe that the concept is without merit. To date, the development of such mortars have focused on 120mm systems, which were tied to larger programs.

A mortar that can be either breech loaded or muzzle loaded, and can be used in either an indirect or direct fire mode, is still worth pursuing particularly for use in the current theaters of operation. The focus should be on 60mm and 81mm calibers. The ability to deny the enemy cover and concealment afforded by brick and masonry walls without having to demolish entire structures or rely on high tech weapon systems needs its day in court.

Leveraging existing technologies to put such a weapon system in the hands of troops today, not five years down the road, is both affordable and low risk technologically. A case in point is the French made Brandt 60mm long-range gun-mortar. Of simple design, the mortar is designed to be vehicle mounted. It can be breech loaded or muzzle loaded while vehicle mounted and used in a direct or indirect fire mode, or ground mounted and used in the traditional fashion. The Brandt uses a wide range of conventional mortar ammunition, as well as armor piercing and shape charge munitions.

Breech-loaded mortar technology is proven and reliable. Suitable vehicles to be used as mortar carriers are in abundance. They can be of simple design like the Bren gun carrier of World War II, the M-50 Ontos of Vietnam fame, the Wiesel 2 currently in use by European allies, or heavier chassis currently in use by the U.S. armed forces.

A lightweight vehicle mounted breech-loaded mortar system, designed to accompanying our dismounted ground troops operating in an urban environment, or in support of remote outposts, would provide immediate direct fire or indirect fire capabilities to small unit leaders at the squad and platoon level.

Commanders could concentrate the fires of mortars from decentralized locations on targets of opportunity, or employ the mortar systems independently, or as part of existing organic fire support assets from a centralized location in support of ground operations. 

In this era of constrained budgets and force reductions, the military should revisit the capabilities of weapon systems currently available. The development of a breech-loaded mortar with direct fire capability would be low cost and of low technological risk given the tried and proven technologies involved.

Technologies developed in pursuit of more costly systems can enhance its capabilities even further. Weapons that can be fielded today are better than systems that may never see the light of day.

William I. Oberholtzer is a retired U.S. Army lieutenant colonel, and works at FFE International.