British artillery - achieved accuracy of fire?

[Chris_Baker]

This is further to my question on the rate of fire that British artillery could achieve (http://1914-1918.invisionzone.com/forums/index.php?s=6c8ff9dfa82a4c6491e04af4cd366a96&showtopic=212156&hl=).

Is there any documented evidence of the accuracy that could be consistently achieved by field artillery? The period of particular interest is December 1914.

[nigelfe]

At that stage map shooting was to all intents and purposes non-existent so fire would have been ranged. Ranging is complete when the shells are falling on the target. The notion of accuracy is therefore irrelevant in this context. Accuracy is the measure of the distance between the mean point of impact and the target centre.

[Chris_Baker]

Understood. But of course not all rounds behave the same, for all sorts of reasons. What I am looking for is some view on this kind of question: 'if a field gun fired 100 rounds on a pre-registered target, how many rounds might be expected to fall within, say, 5 yards of that target'.

[rflory]

Chris: I don't know about the Great War but in the US Artillery today that would be referred to as 'range probable error' (RPE) which is used to establish the accuracy (precision) of an artillery weapon. Range probable error is the range that the weapon may be expected to exceed as often as not. Essentially a large number of rounds are fired from the gun at a constant range and deflection and then the distance from the midpoint of those rounds (where half of the rounds are over and half short) to the most distant round. Range probable error is usually indicated in the firing tables for each type artillery weapon. I don't have any firing tables for Great War artillery but if I remember correctly the US 105mm Howitzer had a RPE of 30 meters and the US 155mm Howitzer had an RPE of 25 meters.

[battiscombe]

As I understand it .. by Dec 1914 much of the field artillery were so worn by overuse in previous battles that they were at times dangerously inaccurate and unreliable. Again, I have seen documents in CRA reports of winter 1914 which may throw some light on this - i seem to remember requirements that guns would shoot deliberately 'long' initially to avoid 'shorts' hitting British lines... and only fire on target once they were sure guns were in fact ranging 'true' [any gunners please excuse the non-technical terminology..], although I would suspect we cannot generalise from Division to Division , or indeed RFA brigade to brigade.. there was some very worn equipment in use which was only gradually being replaced/repaired/serviced... I know 1/KRRC lost men to their own artillery in early Jan 1915

[David Filsell]

The 4.7 inch gun was known as 'strictly neutral' because it's likelihood to drop short. When the 7th Inf Div arty was pulled out of Ypres the variations in range because of wear we're considerable and the tubes projecting from the wire binding.

[nigelfe]

The Range Tables gave the dispersion data, PE in both range and line IIRC, although its just possible I'm thinking mid-war RTs but I don't think they changed in this detail.

I think worn guns would probably increase dispersion due to increased instability in flight, but I've never come across any numbers.

Of course mixed ammo lots would probably have been a bigger factor at that time because it was before they started adjusting propellant loads for variations in propellant energy, given some simple assumptions and RTs (probably later ones) it would be easy to calculate some indicative numbers for this.

The general effect of worn guns is reduced MV and at that stage of the war calibration had not been generally adopted so rounds would fall short, and the type of gun is irrelevant, basic physics applies to all guns. The RGA batteries, at least the regular ones, would have been more likely to have made allowance for this because their battery commanders were more attuned to the problems. Of course a nice hot day could go some way to compensating for the loss of MV depending on what other gunnery processes were being applied.

[TARA]

The comment about the effect of a 'nice hot day' on accuracy makes me wonder if or when the effect of air pressure, wind direction, temperature, etc, was calculated by the gunners in early WWI?

On the subject of ranging/accuracy mentioned in an earlier post, how did the British, German, French, and US, artillery methods compare in WWI? I seem to recall that during the Korean War the US artillery ranged with multiple guns while the British ranged with a single gun. What differences existed in WWI?

TARA

[johnreed]

I am just looking at a copy of Range Table for 18 Pdr MK 1 and 2 at a range of 4,500 yards 50% of the rounds should fall in length 42 yards width 3.8 yards bearing in mind the range tables were compiled based on a new gun which had fired 3 proof rounds and 2 full charges

John

[Chris_Baker]

That is very useful data, John. A linear spread of 42 yards ... and that is only 50% of the rounds fired ... when trying to hit a trench perhaps two or three yards wide ... not good odds, are they?

[petwes]

In 1914 wasn't the majority of ammunition shrapnel so the fuse setting would be another factor maybe?

Peter

[ianjonesncl]

That is very useful data, John. A linear spread of 42 yards ... and that is only 50% of the rounds fired ... when trying to hit a trench perhaps two or three yards wide ... not good odds, are they?

Chris

It would depend upon the position of the guns as to the effect of the linear spread. If you are firing from an enfilade position then the linear spread is along the trench. Obviously the more you move towards 90 degrees the fewer the number of rounds that would hit a trench.

Ian

[nigelfe]

Data and processes for dealing with non-standard conditions were not generally adopted until 1916/7 and meteor messages started being distributed at that time, such notions were a bit revolutionary for RHA and RFA. Of course the pre-war Text Book of Gunnery did explain how to adjust the ballistic coefficient and RGA batteries had such things as barometers, and its reasonably clear that at least some RGA battery commanders did do this early in the war. I don't want to re-write pages from my web site here so I suggest starting at http://nigelef.tripod.com/fc_1914-18.htm for a bit of an explanation of WW1 gunnery.

It also seems some posters aren't up to speed on the difference between accuracy and dispersion, you need to start at http://nigelef.tripod.com/errorsmistakes.htm !

Pretty much any series of identical events has dispersion, including fuze functioning, of course different dispersions affecting the same event will mostly cancel each other out to some extent, although sod's law sometimes cuts in and all the dispersion goes the same way, of course the probability of this happening are very small.

It was a matter for the observing officer to decide whether to range with one gun, a section, or the battery. In WW2 the section was the norm for ranging, when target grid corrections were adopted as standard in 1950 then single gun ranging became the UK norm, but the observer could range with more guns if he considered the terrain was difficult for good observation. Except for moving targets, ranging with a battery was considered a bit of an indicator that the observer wasn't very competent, it was also slower - the big no-no in the UK book. Things like ladder ranging were also used sometimes, but seemingly good ideas aren't necessarily the best in practice.

[TARA]

Having read through the most informative links given in nigelfe's post above, I now have a better understanding of the Gunners and their actions in the early part of WWI. How on earth they operated with the limited technology and worn equipment in such difficult and changing situations amazes me that any level of accuracy/dispersion was achieved! How many today could do this work without a computer?

The work of the School of Artillery improved 'gunnery' methods and techniques during WWI, but how difficult was it to implement new procedures and methods in the field? Pre 1914 most boys left school at 11 or 12 years old and few would have had knowledge of trigonometry, logarithms, etc, so were men (ORs) available for Command/Gun Posts or was all the 'technical work' carried out by artillery officers, who one assumes were better educated?

TARA

[Old Tom]

May I suggest that the ability to hit a trench, or its occupants, may be considered from a different point of view. It is somewhat off topic but I hope is worth the space. The RFA in 1914 considered its task was to provide and to be seen to provide direct support (that may be a modern artillery term, but I only intend a very general point). I do not know if much thought had been given to engaging trenches. If it had, the proportion of howitzers to guns in the division might have been changed. Plunging fire is more effective against trenches and the trajectory of howitzer fire allows a trench to be engaged over the heads of advancing infantry. If this sort of comment has any merit I would start a new topic.

Old Tom

[nigelfe]

The technical work was usually done by the battery commander or perhaps another officer, in the Battery Commander's Post, typically alongside the telephone exchange on the gun position. Obviously this didn't need to start until gunnery started becoming a bit more complicated. The basic procedure for impromptu targets, until 1950, was that the firing data, ie range and switch from zero line, was produced by the observing officer. All the gun end officer did was select the charge. It was only with map shooting that things got complicated, although for air observed shooting in WW1 the piots observations had to be converted into corrections.

Doctrinally, in 1914 indirect fire was the primary method of engagement. Le Cateau was the final nail for those who weren't quite up to speed with the programme and hankered after the 'old ways'.

[Rockdoc]

There was always the correction by observation, too. The Forward Observation Officer and/or a spotter plane would watch the fall of shell and let the battery know the error by a combination of distance and a clock face around the target for direction.

Keith

[nigelfe]

Observing officers (as they were called in WW1) ordered corrections in the form of a new range and switch that was passed straight to the guns. RFC pilots (even if they were RHA/RFA/RGA, and quite a lot were) sent their observations to the BC of the bty they were observing for using the clock code, the BC converted the observation into a new range and switch for the guns. However, I think observers in balloons ordered a new range and switch. Obviously to determine a correction the OO had to see the fall of shot.