Mortar Cannons

2 Inch Medium Mortar

Background and predecessors

As the Western Front in France and Belgium stagnated into trench warfare in late 1914, British forces found themselves with no means of replying to the German minenwerfers (trench mortars) which were lobbing both small and large (over 100 pound) high-explosive shells into their frontline trenches from short range. British commanders requested an accurate short-range weapon which was manually portable in the trenches, could be safely used to attack enemy trenches as close as 100 yards to the British trenches, was easily concealed and projected a reasonably large explosive charge capable of damaging protected enemy positions. The British Expeditionary Force had been expected to participate only in mobile warfare and was not equipped with any mortars.

Various alternative designs for light and medium mortars were evaluated, prompted by the need to get at least some weapon into action without diverting manufacturing capacity from guns and howitzers, which were given priority. Hence the emphasis was on designs for both mortar and ammunition that could be manufactured by small unsophisticated workshops unsuited to other war work :

4 inch mortar

4-inch mortar bomb at the Imperial War Museum

A 4-inch mortar was the only official type to enter service before the end of 1914 (12 units). It fired a 8 pound steel bomb with studs to engage rifling grooves in the mortar barrel, similar to the German minenwerfer. The barrel was improvised by boring out a 6-inch shell. Its range of 900 yards and its accuracy was considered acceptable, but the shell case was expensive and was slow to load. About 40 guns and several thousand rounds were issued by June 1915, with 168 of the total 300 manufactured eventually serving in France. It was soon replaced by the 3-inch Stokes mortar in its "light mortar" class.

3.7 inch mortar

A 3.7 inch pipe gun was an early improvised mortar. 18 were initially made by the Indian Corps in France by December 1914. It was a smooth tube firing a 4 pound "tin-pot" filled with ammonal. The fuze was a length of Bickford fuze ignited by the burning of the propellant, which made it too dangerous for longterm use. By the end of June 1915 another 100 had been manufactured and sent to France and 20 to Gallipoli.

Vickers 1.57 inch mortar

The Vickers 1.57 inch trench mortar was first introduced to France in March 1915, 127 by the end of June, and about 275 were manufactured until it was withdrawn in January 1917 after being replaced by the 2 inch mortar. The 1.57 inch was similar to the eventual 2 inch model, but the particular Vickers design was complicated and expensive to manufacture. It fired either a 18 or 33 pound cast-iron bomb filled with Permite (perchlorate) , but the smaller bomb was considered too light and the heavier had a range of only 200 yards.

The 2-inch Medium Mortar

This was designed and manufactured by the Royal Ordnance Factories in early 1915 and introduced along with the 1.57 inch mortar in March 1915. It incorporated what was known of the German prewar Krupp mortar. This was the first design to meet all the requirements, after modifications to simplify manufacture : it fired a good-sized spherical cast-iron bomb of 42 pounds (total projectile weight 51 pounds with stick and fuze), considered the largest practical size for use from trenches, at ranges from 100 to 600 yards using a simple 2-inch tube as the mortar body; both mortar and ammunition could be cheaply manufactured by small unsophisticated "trade" workshops; the bomb was safely detonated by a standard No. 80 "time and percussion" artillery fuze. Drawbacks were that the steel tail was usually projected backwards towards the firer when the bomb detonated, resulting in occasional casualties; and the No. 80 fuze was also required by the 18-pounder field guns which were given priority, limiting mortar ammunition supply to the front until early 1916 when a special cheap trench mortar fuze was developed.

The 2-inch mortar served in limited numbers in France in 1915 from March, with early mortars and ammunition made by the Royal Ordnance Factory, alongside the Vickers 1.57 inch model. Mass production finally began with an order in August 1915 for 800 mortars from several railway workshops and agricultural machinery makers, together with an order for 675,000 bombs from numerous small firms. This led to the cease of manufacture of the Vickers model, which was twice as expensive, and its withdrawal by January 1917.

It fired a spherical cast-iron bomb "the size of a football" painted dirty white filled with Amatol (identified by a painted green band) or Ammonal (identified by a painted pink band) attached to the end of a pipe ("stick"), hence the nicknames "Toffee Apple" and "Plum Pudding". Weights of bombs as delivered without fuzes varied. Light bombs, from 39 lb 14 oz to below 40 lb 10 oz (18.09 to 18.43 kg), were marked with a stenciled "L". Heavy bombs, above 41 lb 10 oz to 42 lb 6 oz (18.43 to 19.22 kg) were marked with a stenciled "Hv". Hence the total fuzed weight with stick of 51 lb is only an average.

The 2-inch designation refers to the mortar barrel's bore and the projectile stick inserted into it, not the much-larger bomb itself which remained outside the barrel. It was comparable in explosive power if not range to other 4-inch mortars.

The 2-inch mortar was itself superseded by the Newton 6 inch Mortar from mid-1917 onwards. Some Australian units retained them for projecting smoke screens.

Combat use

Typical mortar pit, Mesopotamia 1917, with firing lanyard laid out. The bomb is fuzed.

Deployment

The weapon was initially operated by joint infantry and artillery detachments, eventually it became the responsibility of the Royal Field Artillery. A typical infantry division was equipped with 3 batteries designated X, Y, Z, each with 4 mortars.

Use in action

Its primary use was in cutting barbed wire defenses and attacking enemy front line trenches, such as in the July 1916 attack on the Somme. The spherical shape and relatively low velocity brought the benefit that the bomb did not penetrate the ground before exploding. The short range was a disadvantage as it could only be used if no man's land (between the British and enemy front line) was relatively narrow. It was used to fire some White Star (50%-50% chlorine and phosgene) gas bombs during the Battle of the Somme but only as a stopgap measure until other specialised longer range projectors became available.

Cordite charges appropriate to the required range were dropped into the barrel before the bomb was loaded. Charges and ranges:

1.5 ounces (40 g): 100220 yards (90200 m) (dangerous due to propensity for incomplete burn and hence to fall short)

2.5 ounces (70 g): 180340 yards (160310 m)

3.5 ounces (100 g): 300500 yards (270460 m)

The original design for igniting the powder propellant charge involved the insertion of a standard artillery "T friction tube" into a hole near the base of the barrel. However, the artillery service had a higher priority in receiving the already insufficient number of tubes, so ignition was changed to use a Lee-Enfield bolt mechanism and chamber screwed into a socket in the top of the barrel near the base. A special blank rifle cartridge was loaded and fired via a long lanyard from a sheltered position if possible due to the risk of bombs falling short. This ignited the propellant charge and launched the bomb.

In early use it was situated in frontline trenches but this tended to attract enemy fire onto the troops manning them. Standard procedure became to locate the mortars separately from frontline trenches, in unoccupied trenches or in saps running off the frontline. This had the benefit of drawing enemy fire away from troops manning the front line.

Estimated rounds required for various targets, with instantaneous percussion fuze 107:

Fuze No. 107

Cutting barbed wire: 1 round per 10 square yards (8 m)

Cutting loose wire: 1 round per 6 square yards (5 m)

Destroy trenches frontally: 5 rounds per yard

Destroy trenches in enfilade: 2.5 rounds per yard

Destroy a machine-gun emplacement with top cover not more than 3 feet of earth: 80 rounds

Silencer

Provision was made in mid-1916 for attachment of the "Temple Silencer" at the muzzle, intended to reduce the flash and noise generated on firing, which at the short ranges the mortar operated at was quickly noticed by the enemy and invited artillery response. This required the use of bombs with a special piston attached to the tail which was retained in the barrel by the silencer on firing, and hence sealed the muzzle after the bomb tail left the barrel. This had the major disadvantage of causing the barrel to overheat during prolonged daylight firing, and the silencer was only used at night.

Use as anti-tank mines

British Mk V tank disabled by anti-tank mine, Ronssoy October 3, 1918. Unexploded bombs are visible

In Spring 1918 many of the by-then obsolescent bombs were buried on the Western Front under metal plates as anti-tank mines in expectation of attack by German tanks. This led to some later confusion as to whether unearthed bombs were unexploded mortar projectiles ("Duds") or undetonated mines.

These minefields were inadequately documented. This caused the British problems in the closing months of the war when they had to advance again over territory they had previously abandoned, and also prevented full clearance of the minefields after the war. This led to some French farmers being blown up in the 1930s when they started using tractors e.g. around Gouzeaucourt.

8 Responses to Mortar Cannons

Bob says:

February 24, 2011 at 2:55 pm

Airsoft/Tennis Ball Mortar/Cannon?
I was wondering how i could make ammo for it and how i could build a mortar launcher/ rpg. any suggestions. also it could be a tennis ball cannon also. Helpful: if u could make it out of materials found around the house.

- Self Proclaimed Genius says:
  
  March 2, 2011 at 8:59 pm
  
  Good luck with that!!
  
Jayson Herlth says:

March 8, 2011 at 8:11 pm

hydrogen Air soft artillery, howitzer, mortar, cannon, etc?
Ive been learning about hydrogen and I realized it highly flammable and has a fast burn rate well I was thinking would it be possible to make a hydrogen powered cannon or whatever for air-soft? I was thinking have a large pvc tube and manage a breach load and pre make bottles with wires leading to the inside of the bottle for a safe detonation? ty for any help or suggestions!

Albondigas says:

March 10, 2011 at 2:16 pm

How did Egypt pay for the arms she got from the Soviet Union?
So, Egypt was totally and completely armed by Russians. Egypt had no her own, Egyptian-made tanks, planes, trucks, rifles, cannons and mortars. Egypt did not even have cartridges for the Kalashnikov machine- guns. All, until the last bullet, was provided to Egypt by the USSR.
But it cost billions and billions of dollars.
How did Egypt pay for them? Or she did not?

- blackjack says:
  
  March 10, 2011 at 4:54 pm
  
  “Mainly by its cotton, and fresh vegetable,,, and also some pharmaceutical, and cosmetic products”
  Our short-brained friend Zoser II either has very serious problems with math , or takes us for fools who can not sum 2 and 2 .
  
  A ton of the Egyptian long-staples GIZA cotton cost in the 60s about 2000 US dollars
  Egyptian annual output of the long-staples cotton in e 60s was about 300000 tons.
  Of course, Egypt did not sell ALL of its cotton abroad, and of course, the USSR was not the only client Egypt had. But let´s suppose that Egypt sold all the 300000 tons of its cotton to the USSR.
  300000 tons x 2000 dollars/ton =600,000,000 dollars.
  600 million dollars, this is all Egypt could get for all its cotton.
  
  One Soviet tank T-55, even by the very low Soviet prices, cost 150000 dollars.
  Egypt had 2000 of these tanks.
  The total cost of them to Egypt should be 300 million dollars
  One Soviet MIG-19 cost almost 10 million dollars.
  Egypt had 300 of these MIGs.
  The total cost of them to Egypt should be 3 billion dollars.
  
  Cannons, rifles, bandages, cartridges, bombs, shells, anti-aerial rockets, submarines, naval ships… put it all at another 4 billion dollars( it had to cost at least 2 times more, bet let it be so).
  All in all, about 8 billion dollars. Plus interests, of course.
  
  This is what Egypt had to pay to the Soviet Union for the military technique and equipment it received in the 60s.
  
  The stories about how Egypt paid to the USSR, the then third world cotton exporter, with cotton sound ridiculous. The USSR accepted the Egyptian cotton , because Egypt had nothing more to pay with.
  
  So, the story about how Egypt paid to the USSR with cotton does not fly.
  But how did it pay?
  Very simple; Egypt DID NOT PAY.
  Despite being supplied arms at bargain prices in exchange for cotton, and with long-term, cheap-money credits, Egypt’s debt to the USSR was estimated to be $11 billion by 1977 (AP, (February 11, 2003).
  
  Then, the USSR collapsed, and the new Russian government cancelled the major part of the Egyptian debt.
  By the way, Syria was even more in debt to Russians than Egypt. In the winter of 2005, Syria’s external debt for military deliveries made in between 1955 and 1989 of $13.4 billion was written down to $3.6 billion.
  
  Edit: Loser II, in case you have not understood it with your slow Egyptian brain: the author of the questions makes clear that both Egypt and Israel were getting the military aid, with the only difference being that Israel paid for it- and you did not.
  Another differrence was that Israel had its own tanks, planes, fire-arms- while YOU, with your Syrian friends, lived only on what Russians sent to you.
  It means that Israel can successfully live and fight WITHOUT the American military aid, while YOU without this aid will have to learn to fight with clubs and sticks, like your long-gone forefathers from the caves.
  So, stop your screams about how Israel, armed to its teeth by America, won the war on the “defenceless” and “unarmed” Egypt; you were armed better than Israel, not worse- but Israel beat you up.
  
Smith, John Smith says:

March 10, 2011 at 6:28 pm

Did ships in the 1700′s have mortars or just cannons?

- Girly Brains says:
  
  March 10, 2011 at 7:42 pm
  
  Mortars were used mostly on so-called bomb vessels during this period. For assaulting shore installations, protected harbours and anchorages etc.
  
  They fired a very big ball (the balls themselves varying in composition) in a high parabola with such a charge that the whole vessel was built solely for the purpose, very stable and heavily built indeed, broad beamed, flat bottomed and with sophisticated anchor and winch systems at both ends and sides with which the vessel could be maneuvered into the required aiming position for firing each charge.
  
  They were sailing ships and would sail with the rest of the squadron, but they were not built for speed and could sometimes be left behind with minimum escort.
  
  -|–)
  
Alex S says:

March 10, 2011 at 8:10 pm

difference between cannon and Mortar?
difference between cannon and Mortar

2 Inch Medium Mortar

8 Responses to Mortar Cannons

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