Indirect Fire: A Primer

First shared on twitter.

Indirect fire with the #VickersMG (principles apply elsewhere though): First need to understand that in #VickersMG parlance: DIRECT fire is targets that can be seen from the gun position; INDIRECT fire is for targets that are obscured. Direct fire photos using tangent sight:

A target could be obscured by the terrain (such as a hill, ridge or woodland); smoke or fog (possibly intentional) or the darkness of the night. The #VickersMG is laid on an ‘aiming mark’ and then that becomes its zero line. (Aussie aiming lamp vid)

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The instruments vary over time but the principles are the same: direction dial and elevating wheel; clinometer and bar foresight; dial sight. Only other change is the ammunition used (maybe another thread one day – Mk 7 v Mk 8z).

So, how does it work by #WW2: ammunition trajectory is relatively flat but does lift until the culminating point where it drops again. This results in curved path of bullet which helps increase the range and crest clearance.

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A burst of ammunition creates a cone of fire because the vibration of the gun and miniscule differences in ammunition propellant means all rounds won’t hit the same exact spot. This exaggerates over distance, creating a beaten zone.

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A beaten zone starts as a long-narrow shape, but then gets shorter as the bullet slope is steeper, then longer again as variations become more apparent. The beaten zone makes the #VickersMG (and MMGs in general) area weapons.

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Ranges for the #VickersMG with Mark 8z ammunition (1938 onwards) were considered close if <800yds, effective 800-2000yds, long from 2000 to 4,500yds. Significant reach.

Because of the fire effect needed though, for indirect fire general principle is to have a minimum of four guns and ensure their beaten zones overlap. This creates an effective killing zone that can’t be observed by the enemy.

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This also means that it can’t be observed by your own troops, hence the need for accurate calculations and ranges, so the rangefinder and large-scale maps become important in the planning stages. 

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Setting up four guns means you have a zero line and a pivot gun. All angles and fire control orders are then laid off of the zero line. It can be set up for many more guns, as long as they know their angle of switch. 

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To lay the guns in the first place, they need to be ‘paralleled’. This means they are all pointing in the same direction and the distance between the guns will be the breadth of the gun frontage and lines of fire whatever the range. 

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When paralleling the guns, the dial sight of No. 1 gun is pointed to look at the other guns and they set the lensatic sights on each other. Once aligned, the drums are all set to zero again. Any adjustment from zero will now be the same on each gun. 

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This is why you often see dial sights on guns at very weird angles and in no way pointing towards the target. They’re either pointing at the No. 1 gun or the aiming post.

For targets with a greater width than the gun frontage, you have to allow for a number of ‘taps’ of the gun crosspiece right or left (“2-inch tap”) to distribute fire. You have to use the slide rule or range tables to calculate this.

If the target is narrower, then you adjust the angle of switch for the necessary guns so they fire converges on the target. 

If the target is longer than the beaten zone, you can raise and lower the elevation on the drum of the sight and relay the gun using the spirit level on the dial sight. 

All of this was not taken lightly and was pre-planned using indirect fire charts (sometimes found in war diaries). It was complicated and the officers and NCOs of an MG unit had to be quite adept at completing these schemes quickly.

By the end of the #GreatWar and during the #SecondWorldWar there were mass concentrated barrages with up to 128 guns (Australians!) laid on the same targets or using the same fire control plan. With the correct zero lines and planning, all could switch with ease.

In 1945, a practice of ‘pepperpots’ became a feature of large scale attacks in NW Europe with multiple divisional MG Bns coordinating fire with mortars and artillery to lay down different barrages with different effects. Clever stuff!

We’re planning on recreating the training for this in the next few months so it will all be on youtube.com/VickersMGColle… but I’ll do a quick section during the next Q&A video too. 

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Plenty more on the website, with most of this taken from the 1951 manual which captured all of the wartime learning. vickersmg.blog/manual/1951-ma…

That’ll do for now and hopefully it helps explain the process and the complexity of it for people who are interested. Support us at patreon.com/vickersmg 22/22 (long one! – well done if you made it this far!)

Painting the Vickers MG

In the absence of another place to put this information on the website, this is being written as a blog post rather than a specific webpage. It is cross-cutting so there isn’t a specific category to place it in.

It will be written as a collection of information and references as we come across them, rather than a single coherent article. It should help restorers, living historians and collectors alike.

An overview video of the colour of the Vickers machine gun and tripod for living history purposes is available.

Army Council Instruction 96 of January 1939

This Army Council Instruction notified that “all vehicles (other than limousine staff cars) and all tanks, guns and supporting weapons which are at present painted with service paint shall in future be painted with a standard basic camouflage paint, Khaki Green, No. 3.” It wasn’t to apply to units in Egypt and Palestine. This instruction was amended in December 1939 to show that “unit arrangements” merely meant “unit labour“.

Army Council Instruction 386 of April 1940

To provide additional detail, ACI 386 was issued that set out the requirements for painting specific small arms in camouflage paint khaki green No. 3. For the Vickers MG it included the barrel casing and the exposed surfaces of the feedblock if the feedblock is in gunmetal. The tripod was painted all over except the gun and joint pin bearing surfaces, screw threads of elevating gear and stems of joint pins, and direction dials.

Army Council Instruction 465 of May 1940

This introduced the requirement for disruptive camouflage on vehicles, etc. It’s unclear as to whether it includes small arms but it’s likely that it wasn’t intended to.

Army Council Instruction 1147 of September 1940.

This ACI detailed that machine guns, except Bren guns, were to painted with the Paint, P.F.U. [prepared for use], khaki green, No. 3, heat resisting, special. This was as opposed to the non-heat resistant paint used on mountings and magazines.

Sources

  • The National Archives, WO 293/24, Army Council Instructions 1939.
  • The National Archives, WO 293/25, Army Council Instructions 1940.

One million rounds fired in 12 hours?

On 23/24th of August, it will be 103 years since the 100th Machine Gun Company of the Machine Gun Corps supported the attack on High Wood on the Somme. The story of them firing one million rounds from six guns in 12 hours has appeared throughout written and oral history since then. Did it happen?
It certainly intrigued Rich Willis enough to get in touch with Rich Fisher in Winter 2017/18 and start asking the technical questions about the capabilities of the Vickers, how much water would have been necessary, how quickly did the belt filling machine work and several others. It certainly warranted further investigation as one million rounds is a substantial feat. Rich W sent a draft of an idea for a magazine article to Rich F in February 2018. He’d written it during lunchtimes at work in about a week but it covered many of the pertinent points as he’d gone through the War Diary of 100 MG Company and read Hutchison’s account of the action in his book ‘Machine Guns’ (originally published in 1938 but reprinted in 2004 by Naval & Military Press).
Rich F knew that it had been cited in a lot of books in the Association’s library and found it in Hutchison’s 1919 unit memoir as well. By trawling through a wider range of material it was obvious that this might be suitable for a wider audience and, as it went against a lot of material written by well-established authors, it needed to be published with some credibility.
We investigated it together and did a bit of practical experimentation with the belt filling machine in the #VickersMG collection as well. We soon realised that something wasn’t quite right about the story and looked at it from several angles. Rich F spent some time writing it to fit an academic journal and originally intended to use the British Journal of Military History but that took a hiatus shortly after submission so delayed everything and an alternative outlet had to be found.
This has culminated in an academic article published in the First World War Studies journal of the International Society for First World War Studies. The article investigates the account from the records of the Company, the literature it which it has been cited and from the practical requirements – the logistics – for enabling such an action to take place. It also goes a little further as an example of the challenges when corroborating the accounts of veterans of conflict.
The abstract is:
 
The Great War saw machine gunnery develop from a direct fire weapon through to mass indirect fire barrages. There is an account from High Wood in August 1916 that represents the pinnacle of these developments – firing one million rounds from ten guns in 12 hours. This research examines that account to determine what happened and the technical and logistical requirements of such a feat. By examining the war diaries and characteristics of the Vickers machine gun, it has been possible to identify what actually took place, what would have been necessary for one million rounds to be fired, the potential of Great War machine gunnery and challenge posed when citing first-hand accounts from veterans.
 
If you have academic access then this can be found on the Journal Website.
A copy of the ‘pre-print’ has also been placed on Rich Fisher’s ResearchGate page which includes other examples of work in the same area that he has completed, including a recent conference paper on the logistics of machine gunnery.
A copy of the ‘post-print’ document is also available here for download here.
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We’ll continue to add information about this fascinating account over the next few weeks. Rich Willis has become a Member of the Vickers MG Collection & Research Association and is working on his own research projects as well.
 

UPDATE 21 September 2020:

Rich Willis and Rich Fisher recorded a podcast for the Western Front Association. We talk through the background to the research, what caught our interest and what we found. It’s available here.

How loud is firing the Vickers?

It’s always intrigued me as to how noisy it is to fire the Vickers.  It’s been my view that’s it’s a ‘quiet’ gun for the No. 1 to fire as the cartridge is being initiated almost a metre away from their head.

This has a practical purpose as well, with the Association now able to do function and firing demonstrations for visits to the collection. Not only are there legal requirements about noise exposure, there’s the underlying need to ensure that we protect our hearing. To avoid disturbing our neighbours, the small-scale testing and firing demonstrations are done inside the collection building with all of the doors closed.

Using an application downloaded on my iPhone – so not scientifically accurate but a reasonable indication – I recorded the sound levels while firing.

On the first occasion, I had the phone 2 metres to the front right of the gun at around 1.5 metres off the ground and the other side of a jeep.  This meant that the sound waves were deflected slightly. The maximum sound level was 105 decibels.

On the second occasion, the phone was on my lap in the No. 1 position. It’s worth noting that I was sat on a stool so the phone was actually at the head height of a No. 1 sat on the floor. This recorded only 102 decibels so slightly quieter in this position.

Both of these levels are below the peak sound pressure limit value of 140db and can be easily reduced below the exposure action limit value of 80db for daily or weekly limits if exposed repeatedly. Using standard commercial ear defenders, that the Association has bought for visitors, does this instantly.

I have to consider the variation in production of the PPU blank so I will continue to do these recordings whenever possible and keep the information up to date on this blog. I’d also like to engage a noise professional who can do multiple readings from different places around the gun. This would require an extended piece of firing so this could be a funded piece of research, possibly suited to a student project for an environmental health degree – please contact us if that’s something you could facilitate in any way. It’ll also be good to research it when firing live.

The video below shows one of the firing events from the second occasion when I was recording. From the difference in muzzle blast, it’s possible to see some of the variation in blank as the different amount of gases expended will relate to the noise.


During British Service

From a historical perspective, the British Army has had concerns over the hearing of its troops but I’ve not been able to find any related to machine gunners.

In 1944, Army Council Instructions 732 (June) and 1420 (October) were issued. The October amendment reads:

The discharge of weapons may, in certain circumstances, cause considerable damage to the ears of personnel serving in:-

  • Gun detachments of Field, Medium and Heavy Artillery,
  • Gun detachments of Light A.A., Heavy A.A. and Coast Artillery units,
  • Gun detachments of R.A. and Infantry Anti-Tank units,
  • Infantry Squads for Protectors, Infantry Anti-Tank and Mortars,

when not wearing some form of ear protection.

It is important, therefore, that personnel whose duties take them close to these guns firing protect their ears by plugs of cotton wool.

The 1943 (provisional) manual for the PIAT actually identifies using pieces of flannelette as well as cotton wool.

There were ear protectors issued to civilians with their respirators at the start of the Second World War and it’s possible that these were formally issued later on.

There’s no mention of ear protection for machine gunners but the problem certainly existed and many machine gunners, those who used the Vickers and those since, will have experienced hearing damage from small arms firing – certainly many of the Small Arms School Corps Comrades I have met wear their hearing aids where they didn’t wear their ear protectors.


Sources

How much does a Vickers weigh?

This article isn’t an extension of my previous blog article about light, medium and heavy machine guns, although it’s something I could rant about quite a bit.

When doing an annual ‘spring clean’ of the Vickers collection this month, we had to get all of the guns off of their tripods and give them a once-over.  During this, I noticed that one of the guns felt significantly heavier than the others. It was a Mark I gun that had been converted from a Mark XXI when the Australians no longer required them in their armoured vehicles. It was a 1945 gun so one of the last few made and I thought it would be interesting to compare it with one of the earliest guns in the collection – L 1053 from May 1915.

This immediately showed a difference of 2.7 kg which equates to an increase of 20% over the 30 years of manufacture. Quite remarkable. It made me think what the differences would be on some of the other examples in the collection.

L 1053

An early Vickers Mark I manufactured at Erith in May 1915. It is extensive lightened and features some of the earliest manufacturing techniques. They include the ‘five-arch’ top cover and side plates with extensive machining. This was very labour intensive and the machining reduces over the period of the Great War as production speeds had to increase to ensure that the needs of the army could be met regarding the numbers of machine guns in service. It was also made with the earliest type of fluted water-jacket.

Weight: 13.68 kg.

One of the most noticeable accessories affecting the man-carry of the gun was the Sangster Auxiliary Mounting. It meant the gun could be used without the Mark IV tripod in an emergency. It was left on the gun for the majority of the time as it wasn’t easily removed.

Weight: 17.21 kg (including Sangster Mount).

B 2296

An Australian-made Vickers originally built as a Mark XXI but then converted, in 1945, to a standard Mark I. This meant that the original features of the Mark XXI, which included different filler plugs at the rear of the water-jacket and the pistol grip removed and replaced with a cross-piece. All the guns of this period feature the dial sight bracket as part of the standard equipment.

All of the Australian guns were made with very simply produced components that allowed for mass production. They were made with the smooth water-jacket.

Weight: 16.36 kg.

1186

Another Australian-made gun but this one was a Mark I made in 1939/40. Other than conversation elements from the Mark XXI, it is the same as B 2296.

At the time of weighing, it was fitted with the water-jacket cover and the flash eliminator.

Weight: 17.53 kg (including jacket cover and flash eliminator).

H 5113

This example in the collection was built at the end of the Great War, in 1918, as is one of the early examples of a ‘smooth’ water-jacket. It isn’t, in fact, smooth as some excess weight was machined from the water-jacket, presumably by lathe.

All other components are, visually, the same as later examples and the early machined components are not used at all.

Despite being a Great War Mark I gun, it is fitted with accessories as used in the Second World War. It is used as such for displays with the VMGCRA.

Weight: 16.65 kg (including jacket cover and flash eliminator).

V 6750

The example of a Mark I gun was made at Vickers-Armstrongs in Crayford. It was made in 1943/44 and is quite crudely finished compared to the other examples shown here.

It has undergone some repairs to the crosspiece as it’s believed that this example was in use with airborne forces and has been parachuted from an aircraft.

It is fitted with the water-jacket cover and flash eliminator.

Weight: 17.08 kg (including jacket cover and flash eliminator).

Summary

The variations in weight are affected by the accessories but, given the fact that similar accessories are in use on several of the examples, it doesn’t have a significant influence.

Another factor to consider is that all of these examples are deactivated and this involves some metal being removed and some being added. There may be some variations because of the different people carrying out the deactivation work but unlikely to be significant.

And of course, none of these are filled with any water so that has to be added when considering the weights that the machine gunners had to carry – in this case the No. 2 of the machine gun team.

The table below is a summary of the differences between the different guns, sorted by date of manufacture from left to right and top to bottom.

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Whilst B 2296 is shown as lightest of the smooth water-jacket examples, it’s possible that this was distorted by the lack of water-jacket cover and flash eliminator.

It’s worth adding that the 1914 handbook for the Vickers gives the empty weight as 28 1/2 lb (12.9 kg) so 0.8 kg from the tested weight. It’s more interesting that the 1945 data summary for the Canadian Electrical and Mechanical Engineers (armourers) shows that the weight of the gun is 30 lb when empty. This is 13.6 kg in metric weight and clearly reflects the earlier manufactured guns, not the later. It would clearly come as a surprise to the soldiers who then went on to carry the gun into action.


Sources