6-inch Trench Mortar Bombs

6-inch Trench Mortar Bombs[1]

On 14th May 1915, The Times, published an article, its’ war correspondent Colonel Charles Repington[2], which highlighted the need for “more high explosives, more heavy howitzers, and more men”.

This article reputedly initiated what became known as the “shell scandal”. At the time responsibility for munitions was the responsibility of The War Office, under the control of Lord Kitchener. Partly as a reaction to the scandal, the new coalition Government, under Herbert Asquith, set-up a new department known as the Ministry of Munitions, with Lloyd George as its first minister.

The new Ministry took over responsibility for overseeing and co-ordinating the production and distribution of munitions, from The War Office. It set about the task of overcoming the shell shortage by setting up new factories, converting others and equally importantly they recognised the need for training new operatives.

In early 1917, the original 2-inch medium mortar had been replaced by the Newton 6-inch medium trench mortar, which the firm started producing in late 1917, under the auspices of The Trench Warfare Supply Department. The Department was responsible for procuring and supplying an enormous variety of supplies ranging “from fireworks and grenades to the heaviest form of bombs; also, helmets, shields, specialised chemical apparatus, trench mortars and their ammunition[3].


Newton 6-inch medium trench mortar

It appears that the two parties were still in negotiations as late as 13th November 1917[4]. Due to the heavy demand for mortars, the Department was only interested in those companies that could produce more than 500 mortar casings per week. Despite the firm’s initial stance that they thought that they could only produce around 250 per week, it appears that the Department were eager for the firm to start production. They suggested an initial contract of 13 weeks, with the first batch to be delivered around the middle of December, which the firm were unable to fulfil. The price of 15s. included all necessary plant, etc., to manufacture the casings and dispatch them to one of the Ministry’s filling stations, to be packed with explosive, before being sent onto the front line. It appears that both sides reached an amicable agreement as the Department were anticipating that first batch of 450 mortars would be ready by the 4th January, 1918.



The firm’s munition workers
(Mary Ann Burkenshaw, front row, left)
Photograph courtesy of John Cope   

In early November whilst still negotiating with the Ministry regarding producing the mortar cases, they tried to win a contract to make the crates in which the mortar bombs were to be dispatched. However, the Ministry appeared cautious and took almost six weeks to acknowledge that the quote was too high. This did not stop the firm pursuing the matter, arguing the obvious logistics benefit of one company producing both the mortars and the crates. They also submitted a lower quote, as the Ministry confirmed that the first quote was “very much higher” than others, but all to no avail.



The firm’s munition workers
(Mary Ann Burkenshaw, second row, third from left) 
Photograph courtesy of John Cope   

As late as the second week of December, the firm were still fitting out the shop where they were intending to fabricate the bombs. Despite neither being tooled-up nor having all the relevant knowledge and understanding on how to cast the bombs, the Ministry were pleased with the firm’s progress and were arranging for the vanes to be delivered from a third- party “without delay” to allow them to get their moulding boxes fitted up.


6-inch Trench Howitzer Mark III Engineering Diagram

The firm was obviously on a steep learning curve but was actively seeking advice from those companies already producing the mortars. Once such was James Chadwick (Ironfounders) Ltd., of School Hill Works, Bolton, who responded in early November. The letter was full of practical advice on their method of casting and where to source the various components. The firm wasted no time in following this up and immediately wrote off the various suppliers with orders. All the orders were inevitably slowed up because they had to be either routed through the small tools department at the Coventry Ordnance Works or through the Area Clearing House at the Ministry of Munitions, for vetting and authorisation. This even included the smallest of parts such as three taps; with letters going between the firm, the Ministry and the Ordnance Depot, trying to gain approval. The Brush Engineering Co., Ltd., were already producing the 6-inch mortar bombs and agreed to supply, at a cost of £35, one of their own in-house built machines for “withdrawing the pattern” of the 6-inch bombs. Two such machines were almost immediately dispatched; this time having obtaining the relevant certificates in advance.


The contract with the Ministry was to produce the complete 6-inch mortar bomb ready for filling. However, like several other firms in the same position, the firm bought in several components, only manufacturing the casing itself. On one occasion the vanes were purchased directly from The Crittall Steel Furniture Co., Ltd., of Braintree, Essex and delivered to Loughborough for fabrication. However, most vanes were supplied by Jenks and Cattell, of Heath Town, Wolverhampton.



6-inch Trench Howitzer Mark III

One of the many problems the Ministry encountered was the logistics of handling design changes. With so many contractors, it was not always easy to coordinate. On such occasion at the beginning of December, 1917, there was a design change to the vanes working its way through. Therefore, to ensure a smooth transition as possible, the emphasis was placed on all the firms to undertake the modifications to the old vanes until the new design became available.



In January 1918, the Ministry sent out provisional manufacturing instructions for Mark III/L version:


The body is to be made of good quality grey cast iron, of such a composition that it will not become crystalline or what is technically known as chilled if cast in a permanent iron mould, it must be free from flaws, blow-holes, or other defects, and they must be central to even thickness. The use of chaplets is forbidden. The fuse-hole is to be in the flat end of the bomb which must be bored, screwed and faced to the dimensions shown in the drawing. Two mild steel vanes are to be fixed in the pointed end as shown on the drawing, being placed in suitable grooves formed in the permanent mould or pattern and fused into the bomb when casting. Two bands are to be formed on the parallel part of the bomb, and afterwards accurately machined to the dimensions given on the drawing. The interior must be thoroughly clean and smooth.

Method of Casting

The bomb may be cast in either sand or permanent iron moulds. The cores for the bomb are to be in an iron core box.


These vanes must be pressed out of mild steel plate with slotted holes as shown on drawing T.W.D.5138. The vanes to be would with wrought iron or steel wire made rust-proof, the two loose ends to be taken round the first and last turn three times as shown on drawing. Four stool bars are to be attached to the vanes for stiffening purposes as shown on the drawing.

Screw Threads

Screw threads must, unless otherwise stated on the drawing, be of the form of the British Standard Fine Screw thread and conform to the standard gauges of the Director of Inspection, Trench Warfare.

Contractors may send their gauges at any time to the D.I.T.W. to be checked and compared with the standard gauges.


The bomb before varnishing must stand an internal water pressure of 1000 lbs. per square inch without showing signs.


The interior of the bomb is to be thoroughly cleaned, dried, and coated with varnish of the following composition:-

Shellac……………………………………..3 lbs.

Methylated Spirits…………………….4½ lbs.

Drier Liquid……………………………..12 ozs.

Any bomb supplied in which the metal surface water under the varnish is not often, free from rust, sand or foreign matter or to which varnish does not adhere firmly, will be rejected.


The bomb is to be stamped with the Contractors initials or recognised trade mark, together with the date of manufacture, as shown on drawing T.W.D.5193.


The bomb is to be packed in an approved wood crate, one bomb per crate. The full particulars of crate are given on drawing No. T.W.D.5236A.


The Bomb may be inspected at any time during the manufacture by, and after delivery will be subject to testing by, and to the final approval of the Director of Inspection of Trench Warfare, or an Officer deputed by him.


To be made as and when directed by the Controller Trench Warfare Supply Dept.

Despite the obvious difficulties, the firm managed to get at least one small shipment of mortars bombs off by train to the Trench Warfare Proof Range at The Frith, Harpurhill, near Buxton, before the end of the 1917. They then promised the Ministry that they would be ready for their first large shipment of 500 by the beginning of February. The Ministry duly arranged for the packing cases, stained Van Dyke Brown[5], to be dispatched from Messrs J. Gerrard & Sons, of Swinton, Manchester. However, the bombs were not ready and the Ministry were less than impressed, sending a letter, dated 4th February, highlighting the extreme urgency and insisting that the firm confirm a definite date for shipment by return. Whilst the firm did respond, they claimed that they were still awaiting the packing cases, which the Trench Warfare Supply Department promised to resolve immediately. Whether this was true, a delaying tactic or simply a ploy to win a contract for making the cases is unclear.

In the mean-time deliveries of vanes in batches of 1,000 pairs continued to arrive from Jenks and Cattell. It appears that a couple of mortar bombs were eventually dispatched to Buxton on 14th February and subsequently acknowledged by the assistant inspector six days later. This may have a couple of test bombs intended for inspection.


Having previously agreed a schedule, the Ministry were obviously keen to hold the firm to it. On numerous occasions, they wrote inquiring as to why they have not yet made a delivery and diplomatically asking for an update regarding progress. Despite the non-shipment, the Ministry kept organising both the shipment of vanes from the various suppliers and arranged for a dedicated railway truck to be available at one of the local railway stations, normally the London and North-Western Railway, to the originally agreement delivery schedule.



The first significant shipment was not made until 9th March. Not only was this two months later than originally agreed but the consignment was only 100 mortar bombs, instead of the agreed 450. They were dispatched to the Ministry’s Slade Green Filling Factory, situated midway between Erith and Dartford on the Crayford Marshes, Kent. The bombs were received at the filling station on 18th March, although there was a problem with the way that some of the crates had been packed. Instead of the bombs being placed in the crates with the vanes upper most, they had been the wrong way up, which meant that the lid didn’t fit properly and the bombs were damaged in transit.

By now, the firm appears to getting into full production and on the 21st March dispatched another 300 to Slade Green. These arrived 5 days later, this time undamaged.

Despite being rejected on several previous occasions; they had still not given up hope of securing a contract for making mortar bomb crates for their own bombs. On 25th March, they wrote to the Trench Warfare Supply Department suggesting that by making the crates themselves they would save on both logistics and transit costs, although the latest batch of crates for 2,000 mortar bombs had supposedly just been shipped from the factory of E. Gomme, furniture manufacturers of Leigh Street, High Wycombe[6]. The response from the Department was, surprisingly, both swift and to the point. Firstly, they pointed out that it was “a very simple matter…… to keep you well supplied with crates at present….”. Secondly, the Department were adamant that the firm “would not be able to comply with the conditions of manufacture”. The crates had to be made of home grown timber and the Department could obtain them from Walters & John, of Glentawe Street, Morriston, South Wales, for 1s. 8d. each, whereas the firm’s quotes were two or three times higher. However, the firm was not prepared to give in lightly; they responded the same day, pointing out that they had not received any crates, even though the Ministry had apparently arranged for three sets of crates to be dispatched from Gomme’s. The problems appear not to be related to manufacturing the crates but due to issues on the railways, who were experiencing severe difficulties in getting loads delivered, with everyone experiencing delays.

Once the crates arrived, batches of 300 and 200 mortar bombs were dispatched to Slade Green. It appears that during early April, the Ministry were experiencing a severe shortage of mortars and wrote to the firm asking them to advise the Ministry on the maximum they could produce over the following two weeks. 300 were dispatched on the 6th of April, 200 on the 9th and another 350 on the 19th, all destined for Slade Green.

Such was the progress being made by the firm in increasing production that the Department allocated two railway trucks, instead of the normal one at the end of April. Instead of going to Slade Green, the next couple of deliveries, one of 350 dispatched on 29th April and another of 270 on 4th May were destined for the stores at Crystal Palace.

Despite producing mortars for three or four months, it was not until April that they received their first four payments, totalling £787 10s. 0d.



Somewhat surprisingly there appears a real comradely between the various suppliers, helping one other when problems arose. In March, Messrs Warren Stacey & Co., Ltd., iron-founders and engineers based in Swadlincote, near Burton-on-Trent, were experiencing problems with their castings. The firm went to the trouble of telephoning and inviting them over to discuss the problems and to see how they undertook the casting process.



By the beginning of May, the firm was approaching the end of their initial 13-week contract and wrote to the Trench Warfare Supply Department, seeking a renewal. The Department’s response was that any further contract should see a substantial reduction in price per bomb compared with the first contact. In the Department’s view, the firm should have recouped a significant portion of the set-up costs, allowed for in the price per bomb in the initial contract. Before committing the Department wanted another quote, again covering a 13-week period, detailing not only the price per bomb but the also a committed number. The quote had to include 9d. per bomb, to cover the cost of the vanes, supplied by the Department. However, the Department would allow the cost of the vanes by deducting 1s. per bomb from all bills until all the vanes chargeable had been paid for at 9d. per pair, with an allowed wastage rate of 10 per cent. It appears that the firm’s quote was acceptable to the Department as they continued to manufacture the mortar bombs, despite the occasion hiccup regarding the matching of the delivery of sufficient vanes or crates against the agreed production schedule.



During the three months between May and July, the firm requested over 5,000 pairs of vanes and on one occasion was forced to borrow 500 vanes from Brush Electrical Engineering Co., Ltd., when Jenks & Cattrell ran into inspection issues, resulting in a significant backlog of orders. During this period, most of the mortar bombs were shipped to Slade Green Filling Factory, with the occasion assignment being dispatched elsewhere, such Watford No. 1 Filling Station.



By the middle of July, the Department was keen to talk to about future contracts, so the firm’s London manager arranged to visit their offices. The firm was presumably expecting the discussion to focus on renewing the contract; instead they were told that, along with numerous other firms, they would receive no further contacts. The best that the Department could offer was for the firm to deliver (not produce) as many mortar bombs as possible at the agreed figure of 15s. 6d. before the third contract terminated at the end of September. The Department could buy them from other firms from as little as between 13s. 9d, and 15s.; they were certainly not prepared to pay more than 15s. 6d. The London manager tried to argue the case that it was the Department that made the initial approach. However, the Department were unhappy that not only did the firm take too long to get into full production, but the cost of tooling-up, including alterations to buildings, was excessive. The Department were also unhappy that the price agreed for the second contract was higher than the first and should at least the same, or even less. The final and probably crucial argument was that the Department no longer required the number of mortar bombs previously required.



As recompense the Department suggested that Messenger’s apply to other Departments for work and it was at that point that the firm revealed the fact that had already turned down a contract for making 4½in. Howitzer shells, on the basis that they expected to continue producing mortar bombs. Following the meeting, the firm, whilst trying to finalise the number of mortar bombs they could produce before the contract expired, also considered re-applying for a contract to produce 18-pounder chemical shells as they thought that it was an easier conversion compared with producing 4½in. shells.


Despite the threat from the Trench Warfare Supply Department to drop the firm, the Ministry of Munitions, in fact, cancelled the third contract on the 29th August, replacing it with a shorter 9-week contract for 310 mortar bombs per week. By that date the firm had already delivered 5,500 bombs against the third contract, with twelve going for proof testing, probably to The Frith, Harpurhill, near Buxton. The last shipment for this contract was made on 9th September, when they dispatched 275 to Slade Green. Following this last shipment, the firm immediately set about working on the 9-week contract. However, this was cancelled on 7th November and replaced with another for the same weekly output, this time up to 31st January 1919.



It appears that, in late September, the Director of Projectile Contracts in the Ministry offered the firm a replacement contract to supply 4,000 Mark III and Mark IIIR trench mortar bombs at a rate of 400 per week. The letter, dated 25th September 1918, states “I am directed to request you to proceed with the manufacture of the articles shown overleaf in anticipation of a formal Contract”. Whilst the letter was dated the 25th, the first delivery was meant to have taken place a little over two weeks earlier, on 9th September. In addition, the Ministry was refusing to commit to a price, stating that “The Minister will propose a price at an early date”. This time the Ministry was proposing to charge the firm 10d. per pair of vanes delivered to the nearest station and 2s. 6d. for every lost crate.



With the cease-fire signed on 11th November 1918, it came as no surprise that the Ministry duly cancelled the contract for the weekly supply of 310 mortar bombs. The first letter sent out on 20th November, from the Ministry’s Central Stores Department at No. 28 Northumberland Avenue in London, merely cancelled the supply. A second more solicitous letter from the Ministry of Munitions district office at No. 111 New Street, Birmingham dated 22nd November arrived stating that:

I am requested by the Supply Officer in charge of the above Store to inform you that in view of the present circumstances it is desirable to curtail output, and to entirely cease manufacture as soon as possible without serious disorganisation.

No definite policy has been decided upon as regards fixed number Contracts at present, but you will quite appreciate that every Bomb produced from now means so much wasted labour.

I should be very glad if you would consider without waiting for definite instructions from Contracts Department, the possibility of slowing down, or perhaps entirely ceasing work on these.

An Engineer, from the Office will shortly visit you on the matter, but in the mean-time you would care to let me have particulars of your position, I should appreciate it.



Despite the apparent cancellation, on 27th November Messenger’s received a letter from Mr. T. McNamara, the Section Director of A.M.7 at the Ministry of Munitions in Whitehall, requesting information on the approximate number of bombs that they were anticipating delivering up to the termination of the contract. To which the answer was 1,500 and as the firm had finished casting some weeks previously and presumably this was the number going through post-casting processing. The initial consignments were dispatched to Robin Hood Goods Station, on the East and West Yorkshire Union Railway, presumably for storage at the Patrick Green munitions depot. The last consignment consisted, of 153 light weight bombs for special filling, was sent on 17th January to the Munitions Store 16, at Burton-on-Trent.



Following contract fulfilment came the arguments over non- or delayed payments from the Ministry. The firm wrote to the Ministry in late January 1919, seeking payment for the outstanding deliveries. This was followed up in mid-February by the London manager calling on the Ministry to try and progress matters. On 21st February, the Ministry agreed to pay £1,400, which was half the amount that the firm was expecting. Various exchanges of letters took place over the next few days, with the Ministry stating that they were only paying out on the delivery notes they have received from the firm, and the firm arguing that they had dispatched more bombs than the Ministry was acknowledging.

At the beginning of March, the London manager again visited the Ministry to try and resolve the matter. He came away with a draft for £1,200, with a promise that the remaining £200 or so would be paid in the next 2 to 3 days. There is no record of this outstanding amount ever being paid, although in the middle of April they received further payments of £556 5s. 0d, (£800 less £243 15s. 0d. for tail vanes) for 1,000 mortar bombs delivered as part of the last contract. The firm received a further payment of £145 7s. 0d. on 1st May.



A few days later they returned 823 empty packing cases. In the middle of August, they returned 23 pairs of tail vanes, which were no longer required, to the Depot Manager in Holbrook Lane, Coventry and 35 adaptors to the Deport Manager, at Royds Green, Oulton, near Leeds.

As late as October 1919, the two sides were still trying to reconcile deliveries against receipts, with the firm receiving several further substantial payments.




In late October, the firm purchased 830 redundant mortar bomb packing crates, which the Ministry were simply treating as firewood. Whether these were Messenger’s own crates in unknown as there is no evidence for Messenger’s winning any contractors for making the mortar bomb packing crates; however, they did win several other unspecified contracts for “new joinery work“.



The work of offloading surplus materials continued well into 1920. In January, they sold 73 gallons of Shellac Varnish at 12s. 6d, back to Pilchers’ Ltd., of Morgan’s Lane, Tooley Street, London from whom they originally purchased it.

Selection of Correspondence, December 1919


The dispute with the Ministry over payments was still on-going as late as February 1920, when the firm received a letter from the Liquidator of Projectile Contracts. The dispute appears to have revolved around payment for 531 rectifiable bombs that were delivered as part of the contract for 4,000 bombs that terminated on 26th December, 1918. Messenger’s delivered 3,533 bombs that were accepted, leaving a shortfall of 467 against the contract for 4,000. The Ministry were willing to pay 80 per cent of the contract price for the shortfall of 467 from the 531 rectifiable bombs. This left the firm bearing both the material and manufacturing costs for the remaining 64 bombs, although they were the firm’s own property and presumably they could melt them down and re-use the material. There is no indication as to whether the firm agreed to accept the Ministry’s offer as there is no further correspondence on the matter for further ten months.


Selection of Correspondence, February 1920


The last pieces of correspondence are dated just prior to Christmas 1920, when H.W. Driver of Wilshere, Gimson & Co., chartered surveyors of Winchester House, No. 1, Welford Road, Leicester, wrote to Eric Burder stating that he had that day (20th December) settled the claim with the Ministry of Munitions. This agreement was probably not the outcome that the firm was seeking, which required them to pay the Ministry £475. Whilst there is no specific evidence that this relates to any of the 6-inch mortar bomb contracts, this correspondence is filed within the 6-inch mortar bomb records. Interestingly on one piece of paper someone has written 4-inch bomb, but as this was over two years after the last contract had been cancelled it could simply be a mistake. There is no known evidence in any of Messenger’s records of any contracts for 4in. bombs.


Selection of Correspondence, December 1920



  1. Unless otherwise specifically identified all this information has been obtained from privately held records.
  2. Who was in northern France at the time.
  3. Hansard, 28th June 1917.
  4. Privately held records.
  5. It’s a transparent brown natural earth containing usually over 90% of organic matter. Derived from earth compounds such as soil and peat and positively identified in paintings since 17th century, was extensively used in the 19th Century in both oils and water colour. This colour is found in the pictures of the old masters, among them Rubens, who used it mixed with gold ochre as a warm, transparent brown, which held up particularly well in resin varnish.
    Van Dyke brown
  6. Subsequently became one of the country’s largest furniture manufacturers and in the 1950s introduced the G-Plan range of furniture.