French 75 vs German 77 characteristics Question

[RodB]

I'm reading Hew Strachan's "The First World War" and he states : "Ballistically the French 75 mm was far superior to the 77 mm. Its cone of fire was long, deep and dense compared with the more perpendicular cone of fire characteristic of the German gun... Using delayed action fuses for richochet fire, a 75 mm battery... it was precise in the height at which it detonated : 1.3 metres".

Can anybody explain to me what this cone of fire stuff means, and also how this richochet fire worked.

thanks

Rod

[Old Tom]

Hello,

I think the cone of fire was the pattern of shell impact on the ground when a number of shells were fired with the gun aimed at the same target. However I don't know what was implied by the 'perpendicular'. I guess 'richochet' referred to shrapnel shells and meant that the 75 could achieve better control of the burst of the round so as to have maximum effect. I have read that the 18 pounders of the BEF, or their detachments, did better than the german 77's in that respect.

Old Tom

[Hoplophile]

The many differences between the French 75mm gun (Model 1897) and the German 77mm gun (Model 1896, substantially modified in 1905) were primarily a function of two features: barrel length and recoil mechanism.

The barrel of the French 75 (36 calibres) was substantially longer than that of the German 77 (27 calibers.) All other things being equal, this accounts for the different muzzle velocities of the two pieces (529 metres per second for the 75, 465 metres per second for the 77) and the difference in maximum ranges (without extraordiary measures, such as digging a hole for the trail, the 75 could shoot out to 6,800 metres, the 77 to 5,500 metres.)

The greater muzzle velocity of the French 75 meant that it was more likely to experience something called "range probable error." That is to say, if a 75 and a 77 were set up on a range and each fired a given number of rounds at a single target, the area hit by falling 75mm shells would much longer than the area hit by falling 77mm shells. (As used here, "longer" refers to length along the axis formed by the line of fire of the gun.)

In some cases, a greater tendency towards range probable error was an advantage. If, for example, a gun were set up on a very straight highway (such as an Autobahn) and the target was a long column of troops marching along the same highway, range probable error would be a virtue. In most cases, however, range probable error was a vice. If the target, such as a trench, a barbed wire obstacle, or a skirmish line, was perpendicular to the line of fire of the gun, range probable error was a vice. Put more bluntly, if the job at hand is to drop shells onto a trench, a 77mm would score a larger percentage of hits than a 75.

The French 75 had a much better recoil absorbing mechanism than the German 77. Because of this, the 75 was a more stable firing platform than the 77 and a much higher rate of fire. In open warfare, where a burst of shell fire might play a key role in a battle, this was a huge advantage. In trench warfare, where the name of the game was sustained fire, the higher rate of fire of the 75 provided little in the way of practical advantage.

At the start of the war, high explosive shells fired by the 75 were more effective than those fired by the 77. This was because the French shells contained much more explosive. Later in the war, the Germans solved this problem by putting more explosive into the shells.

The initial limitation on the size of the explosive filling on the German shells seems to have been a function of a desire to give both shrapnel and high explosive shells the same ballistic characteristics. This allowed high explosive shells (which were more easily seen at a distance) to be used for ranging.

[Robert Dunlop]

I don't know if this applied to the 75 but richochet fire did refer to the deliberate bouncing of shells off the ground when engaging certain targets. I have seen this described for the 57mm gun used in A7Vs when engaging ground targets. Az m V delayed time fuzes were used on these shells, which then exploded as the shell ricocheted over the target.

Robert

[MikB]

Hoplophile, that was a really elegant explanation of the quote in the earlier post that I was about to dismiss as pseudo-tech mumbo-jumbo.

There are a couple of points I wouldn't mind going over, though.

Presumably range probable error represents the elliptical footprint of a curved trajectory cone, itself somewhat less elliptical in cross section, intersecting the ground as a plane surface. The additional length of the 75's ellipse is due to the lower angle of intersection because of the higher MV? Is the difference substantial enough to be important?

In a WW1 battlefield, wouldn't the importance of targets in enfilade (if that's the right term), such as communications trenches and forward saps, where the usefulness of range probable error could be exploited to considerable effect, offset their smaller numbers?

Regards,

MikB

[johnreed]

I have a few points to raise:

1 The muzzle velocity is not dependant in the length of the barrel.

2 The ideal propellant will have its all burnt stage whilst the projectile is still in the barrel.

3 Chamber pressure determins the velocity, also the wear of the gun.

As for PEr (Probable Error in range) and PEl (Probable Error in line) see attached atricle.

Probability_Zones.doc

[MikB]

I have a few points to raise:

1 The muzzle velocity is not dependant in the length of the barrel.

2 The ideal propellant will have its all burnt stage whilst the projectile is still in the barrel.

3 Chamber pressure determins the velocity, also the wear of the gun.

As for PEr (Probable Error in range) and PEl (Probable Error in line) see attached atricle.

I think you're completely incorrect on point 1. If you try any cartridge I know of in barrels of decreasing length, it is absolutely invariably the case that velocity will reduce with barrel length. Furthermore, guns designed specifically for high velocity, such as antitank and antiaircraft guns, have barrels typically 50 or more calibres long, while those designed for low velocity, such as howitzers, have barrels typically 20 or less calibres long.

Regards,

MikB

[johnreed]

For point 1 longer barrels means better stability for the round therefore accuracy, not an increase in MV once past the all burnt stage no more velocity could be impated on the round.

I think that the ability to manufacture of squeeze barrels in WW1 was beyond the scope at that time.

John

[MikB]

Pressure must decline after all-burnt, but that doesn't mean it isn't still sufficient to continue accelerating the projectile for tens of calibres of barrel length beyond that point, albeit at a declining rate. The practical limit comes when the engineering and deployment problems presented by a longer barrel outweigh the performance advantages.

Regards,

MikB

[johnreed]

After doing Fall of Shot calibration where the MV's are worked out mathmaticaly (a lengthy and time consuming exercise) and using EVA Electronic Valocity Analyser (EVA) using Doppler Radar The results come out on paper film form, with the timing mark which starts at shot ejection i.e. the round leaves the barrel and cuts an I.R. Beam to start the film. I have never seen the trace of the round deflected upwards that is the MV increasing.

The difference between the French 75 mm Gun and the 18 pdr being.

Calibre Barrel Length Max Elevation Shell Wt MV Max Range

75 mm 36 Cal 18 deg 7.25 kg 500 m/s 8,500

18 Pdr 29 Cal 16 deg 18.5 lbs 491 m/s 6,525

John

27 years a Gunner and proud of it.

[MikB]

Well, I've seen it claimed in a US Army document that the high-pressure gases continue to boost the projectile for a few feet after it leaves the muzzle -

But it's the all-burnt point we were talking about, not exit from the muzzle, and all-burnt invariably occurs some distance before the muzzle, if the charge is to be reasonably efficient and consistent.

And the fact that the 36 cal 75 has a higher MV than the 29 cal 18-pdr tends to confirm that longer barrels do produce faster projectiles - though the cartridges and pressure limits will, of course, be different for these 2 rounds.

Regards,

MikB

[Hoplophile]

MikB, thanks for your kind words.

I think that, before answering MikB's questions, I'll clarify my point about barrel length. I didn't mean to say that barrel length caused either higher muzzle velocity or range-probable error, only that it was 'associated' with those things.

As far as MikB's first question, to wit,

Presumably range probable error represents the elliptical footprint of a curved trajectory cone, itself somewhat less elliptical in cross section, intersecting the ground as a plane surface. The additional length of the 75's ellipse is due to the lower angle of intersection because of the higher MV? Is the difference substantial enough to be important?

In fifteen years or so of reading the German and French literature on the subject of field artillery during WWI, I have not run into any cases where the difference in the horizontal pattern formed by falling rounds gave either the 77 or the 75 a practical (i.e. tactically significant) advantage over its opposite number on the other side of 'no man's land.' In fact, neither weapon was particularly well-suited to the task of bombarding trenches. (Howitzers were a much better means of doing this.) Most of the contemporary discussions I have seen, whether French bragging or German complaining, focus on the issue of range.

That said, I wonder if there was some sort of 'cumulative' effect to the shorter ellipse formed by the falling 77s. That is to say, a 20% (I pulled that number out of the air) reduction in the long axis of the ellipse might not have been noticable when a single battery fired a dozen rounds or so. When, however, a large number of batteries were taking part in a big bombardment, the difference might have been significant.

As far as ricochet is concerned, the French gunners of World War I and the years before were particularly fond of fancy shooting. That is to say, the training of French artillery officers was full of special cases. Indeed, if the memoirs of French artillery officers trained during the war, as well as the various mimeographed lecture notes I found in the US National Archives are any indication, the fondness for such special cases continued throughout the war.

The problems with ricochet fire are:

1. Variable soil conditions. Shells that will bounce on some types of ground will bury themselves in others.

2. Variable topography. Changes in the slope of the ground in question will change the behaviour of the shell.

3. Setting the fuze.

4. Observing the fall of the round. (It is easier to see an explosion that a shell that is skipping.)

Thus, someone firing a 57mm shell at a range of a few hundred metres or less from a gun mounted in a tank might find richochet fire practical. (Being in a tank, he would be very aware of such things as the condition of the soil and the slope of the ground.) Someone firing a 75mm shell a few thousand metres from a field piece, however, would have a much more difficult time arranging for a richochet.

As far as enfilade fire was concerned, it was the 'holy grail' of many WWI gunners, particularly in the early years of the war. (If you can find a copy, check out the 1914 and 1915 volumes of the Royal Artillery Journal. ) As before, however, I have very little anecdotal evidence.

[RodB]

I have a few points to raise:

1 The muzzle velocity is not dependant in the length of the barrel.

2 The ideal propellant will have its all burnt stage whilst the projectile is still in the barrel.

3 Chamber pressure determins the velocity, also the wear of the gun.

As for PEr (Probable Error in range) and PEl (Probable Error in line) see attached atricle.

If I've understood the PE values of 30yds lengthwise and 4 yds crosswise correctly, light field guns were a waste of time in cases like the preliminary bombardmont on the Somme (only 50% of shells falling in a 60 yds x 8 yds box, and presumably only about 2% in the central 2 yards, the width of a trench) - their only value would have been in counterbattery work, i.e. on above-ground targets - similarly the German field artillery was effective in covering nomansland.

In contrast, I read allied reports of 5.9s coming over and being horribly efficient on trenches - is this because they were howitzers ? Moral of the story, you needed howitzers to attack.

Would Bruckmuller's bombardments be based on howitzers and mortars ?

A thought comes to mind - did anybody ever try shooting at trenches diagonally so that the PE lenghwise value was effectively reduced towards 4 yards, i.e. same ballpark as trench width ? But then trenches weren't straight lines were they ? Wouln't the RFA have told Haig "we simply can't hit trenches or wire with the 18 pdr" ?

[johnreed]

To hand I have the Range Tables for a 60 pdr looking at a range of 8,000 yards the 50% Probability Zone is PEr 63.1 yards PEl 10.6 yards PEh 28.2 yards. At that period (WW1) I don't think that they were capable of plotting linear targets, what I mean they did'nt have instruments which came into use after WW1 i.e. The Displacement Calculator which was in use in WW2 when you could engage Linear Targets, not only HE but Smoke. Of course it is not taking into account the wear of the gun because of the huge amounts of ammunition expenditure. Also you will find the 18 pdr firing shrapnel against wire was not particularly sucessful.

John

[Robert Dunlop]

Rod, you may be underestimating the value of light field guns. The 18 pounders played an important role in wire-cutting, along with trench mortars. In the lead up to the Somme, the instanteous fuse was not available. Most of the wire-cutting was carried out with shrapnel.

Counter-battery work was carried out to a limited extent by field guns. The problems with this approach related to the relatively short range and the flatter trajectory, making field guns unsuitable for attacking enemy guns within range but hidden in defilade. I have read of examples where observers for field guns were able to call in fire on relatively exposed German field guns. Also, there are examples where field gun batteries returned counter-battery fire based on the direction of the incoming shells and the distance set on the fuses of the unexploded German shells.

The first day of the Somme illustrated the futility of prolonged pre-bombardments of forward and intermediate positions with anything. Those infantry commanders who appreciated the values of counter-battery fire and the equivalent of the creeping barrage obtained better results. Field guns played a prominent part in the creeping barrages. The mixture of shrapnel and HE, if well controlled in relation to the infantry advance, ensured that the defenders kept their heads down until the attackers were on them. A proportion of field guns would often be ready to move forward to support a successful attack.

Bruchmuller's bombardments included field guns. The principles behind his bombardments included no warning, targeting of command and control structures as well as enemy artillery with gas and HE, suppression of the flanks with persistent gas, targeting of infantry strongpoints, the use of massed minenwerfer to attack wire and infantry positions, and the creeping barrage. Some field guns were then pushed forward in support of the attack.

As the war progressed, field guns came to play a prominent part in antitank measures, on all sides. Several field guns were lost by the British in the opening of Operation Michael because they were positioned too far foward in expectation of German tanks. Some tanks were used in the St Quentin area but they were not significantly engaged with antitank guns.

Robert

[Robert Dunlop]

John, I would respectfully disagree with your comment about wire-cutting with shrapnel. The following was noted with respect to the Battle of Neuve Chapelle, taken from Farndale's history of the Royal Regiment of Artillery:

'Experiments (before the battle) showed that 18-pounders firing shrapnel were very effective in cutting wire and could do it in thirty-five minutes if the fire was very accurate.

Phase one was remarkably successful. The wire, some fifteen yards thick, was effectively cut by fifteen batteries at fifty rounds per gun. The gaps were, in fact, ready within ten minutes of opening fire.'

Re July 1 1916, a Major General John Headlam produced a report entitled 'Notes on Artillery Material in the Battle of the Somme', reproduced in 'Battlefront: Somme', introduced and selected by K Bartlett (ISBN 1 903365 25 2). The report was dated 6 July and covered his analysis of the effects of the preliminary artillery

bombardment before July 1. I quote:

'7. Wire cutting

The German defences on this front were known to be very carefully wired and the specimens attached will show the formidable character of the wire itself. In most cases, it was on iron uprights though in some cases wooden stakes were used.

Wherever it had been possible to obtain direct observation it had been destroyed as an obstacle by artillery fire, and many infantry officers and men told me that they had never been in any way retarded by the wire or ever had to use the cutters on their rifles. The difference in the effect of the different natures of shell was, however, very marked. There is no doubt whatever in my mind that 18-pdr shrapnel is far the most generally effective projectile for this purpose. It sweeps the wire away completely with damaging the surface of the ground and so substituting another obstacle. This was very marked in front of the second line where 18-pdr fire had been used exlusively.

Next to the 18-pdr comes the 2" trench mortar with the Newton fuse. This is also very effective, but not so much as the 18-pdr for the wire is heaped up. In some cases 18-pdr had been employed to sweep

away the wire which had been so heaped up by the 2", and this combination is extremely effective.

But the 18-pdr is not effective against wire on a forward slope (there was a very marked case of this near Fricourt where the fire had been very accurate, but little or no damage had been done to the wire), and there will also be those places where it cannot be reached by a flat trajectory gun and which are beyond the range of a trench mortar. Against such howitzers must be employed, and I was able to examine the effect of this in several places. The 6" howitzer is quite effective in removing the wire, but the craters left are a considerable obstacle to movement. The 4.5" does not appear to have a sufficiently violent explosion for the purpose, the wire being only blown away for a very small radius around the crater, so that there is considerable danger of the result being to increase the obstacle rather than the opposite. But this appears to

be due to the effect of the explosion being confined to the crater. With the new instantaneous fuse (No. 106) I imagine that the effect will resemble that of the 2" trench mortar with the Newton fuse, and if so the power of the artillery to deal with wire will be materially increased.

As regards the nature of wire, it had been anticipated that iron uprights would render the task of the artillery more difficult. I am inclined to think that this is not so. Certainly in several cases the wire was cut away more cleanly and completely from the iron than from wooden stakes - possibly on account of the greater

rigidity of the former. I am inclined to think that the most difficult wire to deal with is that on the iron knife rests as these are simply blown aside by the explosion without being broken up. Gaps can of course be made, but that is all.'

Robert

[Robert Mueller]

That quotation sdurprises me. I have read in numerous accounts how the losses of july 1st were in large part due to uncut wire. I also recall a recent BBC program (sorry, cannot recall the name) where modern evaluations of shrapnel vs HE showed shrapnel to be ineffective. What am I missing here?

Confused,

Robert

[Robert Dunlop]

There were some instances where wire was not adequately cut, as Headlam noted. These instances have been latched onto as a major, or even the major, cause for the failure of the attacks on 1st July. There were much much more serious problems, most notably in the failure to provide adequate counter-battery fire and adequate suppressing artillery fire to get the infantry into the German positions.

One researcher with a particular interest in the artillery (he recently published an account on Uniacke) has noted on a careful study of various accounts that virtually all of the wire was destroyed in front of the German first line. I have not seen his evidence. The wire of the 'second' line was a different story, even though this was included in the objectives for wire-cutting. It could not be engaged with field guns.

Robert

[RodB]

So do we have something of a myth here about the wire not being cut ? I've been reading Lt Col E R Pratt's story on Hellfire Corner (thanks Tom !) :-

Lt Col E R Pratt's mortar fuse

and he claims that he got feedback from those who were there that mortars with his new fuse had cleared wire very well (obviously he is not unbiased).

Reports I've read from German veterans there indicate that the failure on day 1 was due to the attackers being overburdoned and not able to get stuck in as soon as the barrage lifted (i.e. they had to walk, and they weren't right up behind the barrage when it lifted).

[Old Tom]

Hello,

My! This topic has developed and become fascinating. The relative merits of shrapnel and mortar for wire cutting seems to pose another question. I assume the 2" mortar referred to is the one shooting a spherical bomb on a 2" spiggot and that it was HE. If that is so the effects of low velocity HE bombs and shrapnel would be very different. I suppose shrapnel which struck wire where it was supported by a metal picquet would cut the wire and that HE could blow the picquet from the ground. I gather the 106 fuse had that capability. Is this a valid explanation?

Old Tom

[squirrel]

Taking a slightly different direction on this............

I read somewhere recently that shrapnel used on wire was effective if it hit the wire at an angle; that is the shell should burst in front of the wire and the shrapnel balls come down at an angle.

If the shell burst directly above the wire and the shrapnel balls came down straight, very little damage was done.

This may account for the comment on the wire on a forward slope being difficult to cut.

Also seem to remember that the bad weather which caused the attack on the Somme to be postponed made if difficult for the FOO's to observe fall of shot and the damage done. They also had difficulty in spotting damage done by night bombardments if the weather was bad by day.

Just some observations which may or may not be of use to the thread.

[Hoplophile]

While this thread has developed in a number of different directions, the common theme to all of these discussions is the huge variation in the effects that could be produced by the many devices (both shells and pieces) that fall into the category of 'artillery.' At the very least, this should make us wary of the assumption that the art of preparing an attack in trench warfare was largely a matter of stockpiling a bunch of shells and then blasting away in the general direction of the enemy for several days.

[MikB]

...this should make us wary of the assumption that the art of preparing an attack in trench warfare was largely a matter of stockpiling a bunch of shells and then blasting away in the general direction of the enemy for several days.

Yeah, but despite the best efforts of the designers, that was often what actually happened. It took good planning and organisation, consistent ammunition quality, and experienced and alert gunners to make it any different, and they weren't always all to hand.

Regards,

MikB

[BatterySergeantMajor]

The difference between the French 75 mm Gun and the 18 pdr being.

Calibre Barrel Length Max Elevation Shell Wt MV Max Range

75 mm 36 Cal 18 deg 7.25 kg 500 m/s 8,500

18 Pdr 29 Cal 16 deg 18.5 lbs 491 m/s 6,525

John

27 years a Gunner and proud of it.

If you allow me a slight correction? Technically, 18pdr is not a calibre designation, opposed to 75 mm.

Erwin

14 years a Field Artillery man and just as John proud of it.

[28juni14]

This is a most interesting topic, and, if I may be so bold, I would like to add a thought or two. I find the aura built about the "75" often factually suspect. Firstly, the origin of the "long recoil" has long been historically suppressed, but it certainly was not French. ( I can elaborate , but for the sake of space I shall trust most serious students of artillery already know the details.)

Secondly, 20 rounds per minute could be achieved by any of the QF guns in 1914. However, I would ask any knowledgeable gunner, considering the corrosive nature of period powders, if sustained fire of that rapidity would not render a piece derelict after a few moments of such abuse without cooling. Certainly the probability of chamber /barrel burst must increase correspondingly with the rise of metallurgy stress as the heat builds.

Lastly, it is known the Germans manufactured ammunition for captured pieces they were particularly impressed with; Ruskie 7,62cm ,12,2cm, and 15,2cm, and the French 120mm were favorites for the German gunners. Interestingly, though they had caputered hundreds of M1897 pieces the Germans never manufactured it's ammunition. Indeed , more than 300 were comverted to AA use ( 7,7cm L FK L/35(Franz.)), and all were rebored to 7,7cm.

I concluded some time ago that the Brit 18pdr was hardly inferior to the "75", and the Putilov M1902 to actually be superior. I shall now seek cover.....