Aviation & Aerospace - Airpower 2024 - Aircraft by Country - Aircraft Manufacturers Vehicles & Artillery - Armor 2024 - Armor by Country - Armor Manufacturers Infantry Small Arms - Warfighter 2024 - Small Arms by Country - Arms Manufacturers Warships & Submarines - Navies 2024 - Ships by Country - Shipbuilders U.S. Military Pay 2024 Military Ranks Special Forces by Country

Ordnance ML 3-inch Mortar

81mm Light Infantry Mortar

United Kingdom | 1925

"The Ordnance ML 3-inch Mortar of the British Army was an oft-forgotten contributor to Allied actions in World War 2."

Authored By: Dan Alex | Last Edited: 05/03/2019 | Content ©www.MilitaryFactory.com | The following text is exclusive to this site; No A.I. was used in the generation of this content.
Among several of the unsung British war weapons to see action in World War 2 was the Ordnance, ML Mortar, 3-inch. The weapon served throughout the conflict and provided British Army and Commonwealth personnel with the capability to lob explosive projectiles against enemy emplacements and troop concentrations. Initial versions lacked the range of her wartime contemporaries but, as the war progressed, there was little that the mortar system could do, becoming the standardized British infantry mortar weapon until the 1960s.

During World War 1, the British Army relied on their trusted 3-inch Stokes Mortar system of 1917 and it proved a sound weapon well into the post-war years. The interwar years proved a rather slow time for weapons developed in the British military and some casual thought was given to upgrading general firepower at the infantry level. Initially, it was envisioned that a company would be stocked with light machine guns to bring copious amounts of directed firepower into the fold. While this design direction maintained some merit in concert with the popularity of automatic weapons, it would prove a costly venture to produce, not to mention the carrying of machine guns bogging down infantry forces. Instead, the Stokes Mortar design was revisited in the 1920s and evolved into a more modern fighting form. Its 81mm projectile was always a good fit for indirect fire / ranged combat and this was proven time and again in The Great War.

The basic Stokes design was modified into the "Ordnance, ML Mortar, 3-inch Mk II" and production made it possible to see it achieve the numbers required when war officially broke out in Europe to begin World War 2 in 1939. British Army personnel went into combat with the new Mk II model against the forces of the Axis, spearheaded by the well-trained and well-stocked German Army. The British weapon sported an operational weight of 112lb firing a 10lb projectile out to 1,600 yards with a 650 feet per second muzzle velocity and required at least three specially trained personnel in its use.

After some operational experience, a severe design shortcoming came into play, particularly when the Mk II was compared to the German infantry mortar systems (namely the GrW 34 series). The Mk II was simply out-ranged and required British troops to be in very dangerous proximity to the enemy for the system to be able to have any sort of tactical effect on a given battle. German mortars ranged out to 2,600 yards while the British Mk II model could reach just 1,600 yards in ideal conditions - a 60% difference in comparison. British engineers, therefore, went back to work on improving the Mk II design.

A period of reworking and testing followed by intense evaluations produced a new 3-inch mortar form with a lengthened barrel, new projectile with increased charge and inherently longer operational ranges (up to 2,800 yards). Within time, production supplied the demand and British troops now fought on equal footing with their Axis counterparts. For the interim, British infantry and Commonwealth Forces were relegated into using captured German or Italian mortars as well as their applicable ammunition stores while the Mk II was being reworked.

As the war progressed, the British 3-inch Mortar was further addressed to include a new sighting system as well as a revised baseplate. A more portable form was also developed to be used by paratroop elements and some were dedicated for use in the tropic and mountainous environments in the Far East where the British Army and Commonwealth Forces tangled with elements of the Japanese Empire. In the end, the British 3-inch Mortar proved a reliable and robust weapon system, cleared of all limitations seen in the initial production model and revised for the better. Crews soon learned the strengths of their 3-inch mortars and could even finagle a minimum range of 125 yards if required while playing with elevation and propellant charges to fine tune the mix. This short range performance could prove ideal in close-support actions against advancing enemy troops.

Article Continues Below Advertisement...
Design-wise, the Ordnance ML Mortar 3-inch was of a basic arrangement and conventional in function. The design was characterized by its major components - namely the launch tube, baseplate, bipod, sighting equipment and ammunition. The system was 81mm (3.2") in precise caliber (despite the 3" used in the official designation)) and cleared to fire a standard High-Explosive (HE) projectile as well as smoke and illumination rounds. The mortar measured in at 1.295 meters long while the barrel made up 1.19 meters in length. When made ready to fire, the system weighed in at 126 lb while, when broken down for transport, the weapon required at least three personnel - each charged with transporting one of the major pieces into combat. The weapon's elevation as limited from +45 to +80 degree angles of fire and traverse was 11-degrees in either direction. Elevation and traverse controls were mounted on the bipod assembly while the sighting device was identified along the barrel, towards the muzzle end. The 81mm projectile weighed in at 10 lb apiece.

Operation was conventional with personnel sighting the weapon against the intended target area. One member then dropped the ready-to-fire projectile in through the muzzle to which the projectile fell down the launch tube and struck a firing pin at the baseplate, igniting the internal charge propellant. This explosion forced the projectile out of the tube and along a rudimentary flight path. Crews could then revise the traverse and elevation based on where the previous round fell and repeat the process all over again. The heavy baseplate served to retard the inherently violent recoil of such a weapon while also serving as a third support leg in conjunction with the bipod assembly. As an "indirect fire" weapon, the object of the mortar was to target areas as opposed to individual enemy forces. Its High-Explosive projectiles were very useful against concentrations of enemy personnel. Smoke rounds could be used to shield friendly tactical movements while illumination rounds were used in low-light settings to mark enemy positions.

Typically, the 3-inch mortar system was carried into position by mortar team personnel but it was not uncommon for the British Army to make use of their nimble little "Universal Carrier" tracked vehicles (detailed elsewhere on this site) in transporting the weapon at speed (note that the 3-inch mortar was not designed to be fired from the vehicle itself and had to be unloaded and setup to fire on the ground). This speedy transport allowed mortar teams the capability to reach a given area quickly, complete with ammunition supply in tow, and disembark to setup the mortar and make it ready to fire. A crew could also dig out the surrounding land and create a ground depression from which to fire from, providing the crew with basic protection from enemy return fire. So long as the ammunition supply was forthcoming, the mortar team could supply a steady rate-of-fire over the heads of friendly troops. The 3-inch design could also be dropped into action via parachute within hardened containers in three main sections - the barrel and bipod, the baseplate and an initial ammunition supply. Paratrooper elements need only recover the various parts, assemble the weapon and begin firing on enemies.

The Ordnance 3-inch mortar went on to serve beyond the United Kingdom, seeing service within the inventories of Australia, Canada, India, Ireland, Luxembourg, New Zealand and the Philippines. In the Philippines, the 3-inch mortar saw combat actions with counter-Japanese insurgency forces during its occupation during World War 2 and served into the 1960s. The wartime 3-inch mortar was inevitably replaced by the modern UK/Canadian joint design effort L16A1 81mm mortar beginning in 1965.

Content ©MilitaryFactory.com; No Reproduction Permitted.
The physical qualities of the Ordnance ML 3-inch Mortar. Information presented is strictly for general reference and should not be misconstrued as useful for hardware restoration or operation.
1 mm
0.04 in
O/A Length
1 mm
0.04 in
Barrel Length
126.10 lb
57.20 kg
Manually-Fed; Pin-Actuated
81mm (3.2-inch)
Single-Shot; Reusable Tube
Integrated Optics.
Performance specifications presented assume optimal operating conditions for the Ordnance ML 3-inch Mortar. Information presented is strictly for general reference and should not be misconstrued as useful for hardware restoration or operation.
8,250 ft
2,514.6 m | 2,750.0 yds
650 ft/sec
198 m/sec
Muzzle Velocity
Notable series variants as part of the Ordnance ML 3-inch Mortar 81mm Light Infantry Mortar family line.
Mk I - Original mark of 1917
Mk II - Base Series Designation
Global customers who have evaluated and/or operated the Ordnance ML 3-inch Mortar. Nations are displayed by flag, each linked to their respective national small arms listing.

Contractor(s): Royal Ordnance - UK
National flag of Australia National flag of Canada National flag of India National flag of Ireland National flag of Luxembourg National flag of New Zealand National flag of the Philippines National flag of the United Kingdom

[ Australia; Canada; India; Ireland; Luxembourg; New Zealand; Philippines; United Kingdom ]
1 / 1
Image of the Ordnance ML 3-inch Mortar
A Canadian mortar team at work with their Ordnance ML 3-inch in 1944; color

Design Qualities
Some designs are single-minded in their approach while others offer a more versatile solution to requirements.
Some designs stand the test of time while others are doomed to never advance beyond the drawing board; let history be their judge.
Going Further...
The Ordnance ML 3-inch Mortar 81mm Light Infantry Mortar appears in the following collections:
Disclaimer | Privacy Policy | Cookies

2024 Military Pay Scale Military Ranks U.S. DoD Dictionary Conversion Calculators Military Alphabet Code Military Map Symbols US 5-Star Generals WW2 Weapons by Country

The "Military Factory" name and MilitaryFactory.com logo are registered ® U.S. trademarks protected by all applicable domestic and international intellectual property laws. All written content, illustrations, and photography are unique to this website (unless where indicated) and not for reuse/reproduction in any form. Material presented throughout this website is for historical and entertainment value only and should not to be construed as usable for hardware restoration, maintenance, or general operation. We do not sell any of the items showcased on this site. Please direct all other inquiries to militaryfactory AT gmail.com. No A.I. was used in the generation of this content.

Part of a network of sites that includes Global Firepower, WDMMA.org, WDMMW.org, and World War Next.

©2024 www.MilitaryFactory.com • All Rights Reserved • Content ©2003-2024 (21yrs)