Artillery Fire Direction Calculations

[jwduquette1]

It demonstrates a fundamental lack of understanding to compare HESH from tank with HESH from a field gun.  The key difference is the fire control technology, most guns haven't moved on very far from WW2 technology.  I don't think tanks were very good at hitting targets at 5000m at that time either!  Even the best atk guns with HV shot were hard pressed much above 2500m, and that wouldn't be a moving target.

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This really doesnt answer my question. If you are crewing an artillery piece and your shooting at a target 5000m away why am I supposed to believe that having a direct line of sight to the target is going to result in a less effective shoot than if I can't see the target and its 5000m away? So yes your right -- I do have a fundmental lack of understanding of the logic your employing here.

[Paul G]

[nitpick] UP and DOWN are perfectly acceptable when adjusting VT and Illumination [/nitpick] 

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[nit-nitpick]Range and deflection errors are always ADD, DROP regardless of munition. You are refering to HOB corrections, and VT is not adjusted for HOB as it is automaticly set to detonate at 20m altitude, Mechanical Time (MT) fuses are however.[/nit-nitpick]

[Paul G]

This really doesnt answer my question.  If you are crewing an artillery piece and your shooting at a target 5000m away why am I supposed to believe that having a direct line of sight to the target is going to result in a less effective shoot than if I can't see the target and its 5000m away?  So yes your right -- I do have a fundmental lack of understanding of the logic your employing here.

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If you are crewing a howitzer and can direct fire at a target 5000m away, you are very poorly situated!

[jwduquette1]

If you are crewing a howitzer and can direct fire at a target 5000m away, you are very poorly situated!

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Ok -- I'm poorly situated. I am still crewing that poorly situated artillery piece and shooting at a target 5000m away. My direct fire telescope reticle is graduated to ranges of whatever -- let’s say 3000m. What differences in mechanics are there in establishing my quadrant elevation for direct or indirect fire at 5000m?

[DKTanker]

[nit-nitpick]Range and deflection errors are always ADD, DROP regardless of munition.  You are refering to HOB corrections, and VT is not adjusted for HOB as it is automaticly set to detonate at  20m altitude, Mechanical Time (MT) fuses are however.[/nit-nitpick]

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Let's call it a draw on the nitpicking

[DKTanker]

Assume for a second you are crewing an artillery piece; Why would indirect fire be any more effective than direct fire -- same range for either mode?

Obviously I've never made that ridiculous claim. For those that have, I have but one question, why would anybody ever direct fire if indirect is more accurate. The answer lies in what FA considers a hit, anything within 50 meters is considered close enough.

Regarding the stories floating about on this forum about tanks accurately shooting HESH at tank sized targets 5km away and consistently getting 1st, 2nd or even 3rd round hits -- in your experiance is this BS?

 

Regards

JD

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I think I've/we've diplomatically stated as much. In as much as the round to round dispersion for HEP/HESH is greater than the size of tank at 5000 meters, it is hardly credible to state that consistent effective aimed precision fire at 5000 meters is possible. I'll not say that someone couldn't possibly hit a target with HEP/HESH at 5,000 meters first round, the law of averages says yes they can. That being said, the law of averages explicitly implies that luck is involved.

Edited June 3, 2006 by DKTanker

[nigelfe]

The amusing thing is that I did once control the fire of a 105mm How, standing alongside it, against a tgt some 10km away. And yes this was ops not trg, under tight RoE and only allowed to fire a handful of rds. The target was very surprised and scarpered with considerable alacrity, and no one went that way again (in daylight).

 

We didn't have any met data, but did correct for other variations for non-standard conditions, not least non rigity (technically speaking, for the nitpickers, it isn't a non standard condition), which since we were some 1500 ft higher was not insignificant! So yes, if the guns can see a target directly then its reasonable to use what in effect are a combination of direct and indirect procedures. However, it's only in exceptional circumstances, either deliberate (my case) or very bad planning or the enemy is getting you by the short and curlies that long range direct fire by arty is an option.

 

I guess the first point to remember is that tks aren't arty and arty doesn't try to be tk. Arty is in the business of fire-power mobility, being able to attack any target in ranging without having to move (or to see it directly).

 

Direct fire atk, which is what a grateful tax payer provides HESH for, is a local defence matter. And tks usually have better protection, mobility and direct fire sights than guns. In these conditions guns have to assume they aren't going to get two bites at the cherry, so shooting at short range or whatever the best chance of a first round hit is, is the rule. Hence you don't want to encourage premature engagement by going up to 5000m in the HESH FT.

 

I'd like to think that I don't need to make the point that you can also use the dial sight for direct fire, and if you're shooting HE that's what you use.

 

The next point is that arty isn't in the business of 'direct hits', because probability is against it, if you want that then there are 'destruction' procedures. These work and are very good if there's an obliging enemy who digs their tanks in and leaves them there. In Italy in WW2 one GE corps reported it was their main source of their tk losses, the Brits were using 5.5 and 7.2 with air OPs.

 

That said, while 105mm, 203mm and most 155mm have a rg PE of about 12 m at 5000m, some modern 155mm are down to 5m at this range. What this means is that with these guns, which have a burst fire capability (3 rds 10 secs), and if all the other elements of the arty system are in place, then if a tk is kind enough to stop for a couple of minutes within about 5km of a gun there's a good chance they're going to be hit by a 45 kg shell holding 11 kg of HE. If nothing else it will be an interesting experience.

[jwduquette1]

Obviously I've never made that ridiculous claim.  For those that have, I have but one question, why would anybody ever direct fire if indirect is more accurate.  The answer lies in what FA considers a hit, anything within 50 meters is considered close enough.

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I wasn’t suggesting that you had said this – this goes back a page or so in this thread. I was simply asking why it is on the one hand ridiculous to conduct direct fire shoots at targets that are beyond the range limits of the direct fire telescope on an artillery piece, yet not ridiculous to conduct indirect fire at a similar target at the same range.

 

I think I've/we've diplomatically stated as much.  In as much as the round to round dispersion for HEP/HESH is greater than the size of tank at 5000 meters, it is hardly credible to state that consistent effective aimed precision fire at 5000 meters is possible.  I'll not say that someone couldn't possibly hit a target with HEP/HESH at 5,000 meters first round, the law of averages says yes they can.  That being said, the law of averages explicitly implies that luck is involved.

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As to the 5000m(+) HESH thing, I think I did make an attempt to run the dispersion thing up the flag pole. Showing how large the 50% and 100% Zones are for a HESH shot at this sort of range. As I recall I received answers along the lines of “scientists have proved that bees can’t fly” and similar banter.

Edited June 4, 2006 by jwduquette1

[jwduquette1]

The amusing thing is that I did once control the fire of a 105mm How, standing alongside it, against a tgt some 10km away.  And yes this was ops not trg, under tight RoE and only allowed to fire a handful of rds.  The target was very surprised and scarpered with considerable alacrity, and no one went that way again (in daylight).

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All the previous banter and finally the answer I was looking for. Can you elaborate a bit more on this -- like when and where this occurred -- circumstances that allowed this sort of extraordinary line of sight, what sort of optics you were using, etc.

[nigelfe]

So you want war stories?

 

late 65 or early 66, can't remember exactly. On the border ridge in what was then called the 5th Division of Sarawak, target was 10km (and a bit) inside Indonesia. It was a permanent Claret operaion, I believe the only one.

 

It was just convenient to use the dial sight in direct fire mode and make an RT correction for drift because the sight could see over the gun pit wall to where the target was for line (no way they could see the men but the lie of the ground was disticnt enough. However, I ordered the range and had the benefit of king size tripod mounted binos.

[jwduquette1]

What the hell? Indonesia? Were you fighting Communist guerillas or something? I am totally unfamiliar with this war. Pretty obscure.

 

On optics bit -- I mean were you using a BC scope or an uber powerful set of binoculars to direct the shoot?

[jwduquette1]

I had referred to this earlier. This story has been repeated in various forms in several books. The presentation is typically slightly different between various authors – creative license I suppose – but the gist remains the same. I would imagine various folks can easily find faults with some aspects of Forty’s technical presentation, however the end result is still tanks destroying point targets at extreme ranges with what appears to have been fairly low ammunition expenditures. So what is going on here? What’s the trick? Dispersion tells us ammunition expenditures required to secure direct hits should be fairly high for these sorts of shoots?

 

I scanned this from:

 

George Forty, “Tank Action, From The Great War to the Gulf”, (Pages 246 – 254) Sutton Publishing Book, Copyright 1995.

 

Any errors in the text are from my own scanning and OCR.

 

A Strange Battle

 

Thirty years ago the Israeli Armoured Corps fought one of its strangest battles. Over a period of months specially selected tank crews fought a 'precision war' against Syrian attempts to divert natural water resources on the Golan Heights. If such attempts had succeeded the very existence of Israel would have been threatened as her survival depended, and still does depend, upon these waters.

 

On the same day as Maj Gen Tal took over the Armoured Corps in 1964, Maj Gen David Elazar took over command of Northern HQ. It was a period of high tension on the Syrian front, during which Syrian forces, in dominating positions on the high ground above, fired repeatedly on Israeli patrols moving in the valley. Only a few months earlier Israel had started the flow of water through its 'National Carrier', a conduit which carries water from the Sea of Galilee down to the barren Negev Desert in the south. The Arabs were in uproar, Syria demanding war, but Egypt showing reluctance, still cautious after the embarrassments of the recent conflict over Suez (Operation 'Musketeer'2). An emergency joint Arab conference resulted in a plan to divert the sources of the River Jordan, in particular the Banias springs on the Golan, thus nullifying the Israeli project. At the same time Syria began building a carrier of its own, aimed at diverting the waters into Jordan, protecting this work with a series of fortifications along the Golan Ridge, which dominates the entire region.

 

Gen Elazar, watching the Syrian progress from a vantage point near Tel Dan in the northern sector, contended that tank guns should be able to hit point targets on the Syrian water carrier and to deal with enemy fire coming from dug-in tanks. Some senior Israeli commanders expressed doubts, but Lt Gen Yitzhak Rabin, then Army Chief of Staff, gave his consent and a company of Centurions from the 7th Armoured Brigade (7 Armd Bde), commanded by Capt Shamai Kaplan,3 was sent to Tel Dan to deal with the situation. 2nd Lt Avigdor Kahalany, who was commanding a Centurion troop in this company, was the first into action. They watched as an Israeli mobile patrol moved along a dirt road in full view of the Syrians. Suddenly, at a range of about 800 m, it was engaged by Syrian machine-gun fire from two vintage Second World War ex-German PzKpfw IV tanks, which had been dug-in, with just their turrets visible. Lt Col David Eshel, a well-known writer on the IDF, told me:

 

'Within 5 minutes Kahalany's Centurions were in position, well dispersed at 50 m intervals ready to fire. Kahalany's tank was first to fire, aiming for some Syrian recoilless guns placed in the shadow of one of the houses above. The air filled with flying shrapnel, screaming tank shells and clouds of smoke. Syrian mortars pounded the area, while the Panzers joined in. The Centurions fired nonstop for almost an hour before a cease fire was arranged by UN observers.'

 

Unfortunately, what became known as the 'first Nukheila 'incident' ended in complete failure. Having fired nearly 100 rounds the Centurions' 105 mm guns had hit very little and no Syrian tanks had been knocked out. Gen Tal, who came to investigate, was naturally furious. Gen Rabin started to have second thoughts about the whole idea, but Tal was adamant that he could deliver the goods. He immediately called a meeting of all Armoured Corps officers above the rank of major and did not mince his words when he addressed them. A new gunnery training camp would be set up in the Negev, where all tanks crews, in particular gunners, would be subjected to gruelling schedules, firing hundreds of rounds until they could guarantee to hit with the first round at any range. Tal spent many days and nights with his men on the ranges, monitoring their progress. Eshel again: 'Blessed with great technical talent and a stickler for detail, Gen Tal was a hard man to please when it came to tank gunnery. He soon knew every gunner by name.' The results were quickly proven when, only two weeks after the initial failure, Tal was ready to prove his point. Kahalany's Centurions were again put into position, but this time in a secondary role, while a platoon of Israeli-modified Shermans was selected to do the primary job. These had been upgunned locally with the French CN 75-50 gun, which was based upon the German 7.5 cm Kwk 42 (L/70) which had been mounted in Panther. The gun was preferred by many Israeli tank crews, who had initially found Centurion, with its original 20-pounder gun, totally ineffective. However, the Centurions had now been locally upgunned with the British L/7 105 mm gun, which at the time was the best tank gun in the world. Tal, who had examined the British gun personally, was delighted with its performance and shook off the doubts of the veteran Sherman crews, who still swore by the French gun. Kahalany was also confident that his Centurion was ready to prove its worth. His gunner, Sgt Shalorn Cohen, was the best he could get and had delighted Gen Tal with his performance on the ranges. Col Eshel writes:

 

'As noon came, the patrol was passing along the dirt track leading towards the springs and soon the Syrians opened the day with machine-gun fire followed by light mortars. Capt Shimon's Sherman platoon was quickly out of its hiding and opened fire, but misfortune hit one of the tanks which slid into a ditch. Kahalany saw the accident and ordered his own Centurion up into position. At 800 m his gunner Cohen took aim and sent his first high-velocity round towards one of the Syrian Panzers hiding in a dugout, which presented a target only 60 x 120 cm. It was a difficult target to hit even at that range at a time when advanced optics were not available, as they are for tank crews today. But Cohen fired and his rounds hit home, the Syrian tank exploded into searing flame. Encouraged with his success, the gunner fired again, taking extra care that his aim was on the mark and the second Panzer burst into flame.'

 

Soon a fierce battle was in full swing, with Syrian artillery pounding the nearby settlements and' the Israelis calling in fighter bombers to s/ilence them, until the UN arranged a cease-fire.

 

Tal's tankers had done a good job, but there were still doubts among some senior officers as to the effectiveness of tank fire to silence Syrian point targets. However, the water problem did not diminish and it was clear that something had to be done. Failing a solution, the Israelis would be forced to give in, or would have to escalate the matter to full-scale war. Gen Tal was convinced that high-precision tank gunnery would answer the problem, by destroying the Syrian equipment without having to resort to such drastic measures. He had carefully studied the potential of contemporary tank guns and was convinced that they had far more potential than the technical parameters set by the designers. He contended that the first failure had been the result of insufficient training by tank crews and not lack of quality material. So far, current training standards had allowed tank gunners to fire with limited accuracy at ranges of not over 800-1,000 m, a hit within a 4 m target radius being considered sufficient, assuming that ricochets would also be lethal. Gen Tal was totally opposed to this theory, stressing that only point targets should apply in tank gunnery and that engagement ranges should be extended to 1,500 m. A major retraining was now under way, which included both regular and reserve tank crews. Eshel writes:

 

'. . . professional skill becoming in high demand and emphasis placed on specialization rather than a wide range of skills which were formerly demanded. Thus a specialist bore-sighting team was given the task of zeroing all the tanks with high precision equipment and test firing, thus bringing every single tank to a common denominator in combat. One of the men chosen to serve in this coveted unit was Shalom Cohen (later Sgt), who thus fired a huge amount of rounds amassing great experience which would serve him well later.'

 

Despite the Israeli success in the second engagement, the Syrians had clearly decided not to give up. However, they did move their working sites eastward, until they were some 2,000 m from the nearest Israeli positions in the valley, a range at which their experts assumed they were invulnerable to the Israeli tank guns. Without any of today's high-pressure guns, supersonic high-velocity ammunition and ultra-modern optics, such engagement ranges were considered impossible for tank gunnery. Indeed, to hit a precision target at any range above 1,500 m was thought to be a tanker's dream! Eshel again:

 

'Gen Tal was faced with two alternatives: one was to use the indirect or semi-indirect firing method, which was used in the Italian Campaign during the Second World War by Sherman crews firing HE shells from the short 75 mm gun usually uphill and in salvoes. But apart from a few Israeli officers who had been taught this practice in France in the early fifties, no one in the IDF had so far fired in this method. Moreover, indirect firing would not guarantee accurate hits on point targets, which was the prime requirement here.

 

'Thus a more reliable firing procedure had to be founds to destroy point targets at long range by direct firing practice. Direct fire, apart from direct laying - in which the target is visible from the gunner's optics - is used when the target is visible from the position of the gun barrel or the fire base. Thus the projectile travels along a straight path trajectory, the gunner setting his reticule as ordered by the commander. But at Tel Dan in the Northern triangle of the then demilitarized zone, the topographical situation introduced an even more intricate matter into the equation. Studies revealed that from a ballistic standpoint, firing uphill would actually increase hit probability substantially, than firing over a straight line of sight. Moreover, aiming uphill also increased the probability of placing the target within the gunner's optics - than actually firing with direct laying. The same would apply to firing downhill, as long as the depression of the gun allowed this (which was not the case with Soviet-built tanks). The ballistic phenomena was little known throughout the professional world, due to the fact that tank gunnery normally applied to combat ranges and worried little about unusual practices of firing at longer ranges which were thought impractical and were given to other forces to deal with, such as air power with airborne guns and rockets, or artillery barrages. Here, due to political restraints, it was up to Tal's theories to solve a strategic problem with his tank guns, which, if successful, would not only destroy the Syrian diversion project, but would also prevent a dangerous escalation to the brink of full-scale war over the issue. The responsibility that Gen Tal and his experts faced was tremendous. It was the first time in military history that tanks were given a strategic task to perform and if he failed there would be no other option but to go to war or give in.'

 

Naturally Tal wanted to test his theories as carefully as possible, so he fired a large number of rounds on the Negev ranges over a specially designed model. The results were excellent and he was soon convinced that he could do the job.

 

Tal had proved beyond doubt that rounds fired at high angles of incidence were more accurate than those fired at the same long ranges over a straight line of sight. Thus, firing uphill at the Syrians on the slopes of Mt Hermon would be ideal. However, Gen Tal had to convince his superiors, who still based their views on the dismal past showing of the first encounter. The chance to prove his theories came on 6 March 1965, four months after the last incident, when a Syrian recoilless gun fired on an Israeli tractor near Almagor, killing the driver. Although it had nothing to do with the water diversion project, Gen Tal seized on the opportunity to convince the doubters once and for all. He personally boarded a camouflaged Sherman, mounting a 75 mm French high-velocity gun, of the type which had already proved itself in the last fire fight. He could clearly see the Syrian gun crew preparing to fire at another Israeli tractor which was starting out along the disputed patrol track, with a volunteer driver.

 

'This was the cue for which the General had been waiting,' writes David Eshel, 'his first HE round scored a direct hit and the enemy gun exploded into fragments, clearly seen by the senior officers watching the scene from a hill nearby.' Encouraged by this success, Rabin talked to the Prime Minister, who authorized Tal's plan and a few days later Gen Tal, together with some of his officers, flew north to co-ordinate the plan with Gen Elazar. The final show-down would be at the current Syrian water diversion site, on the slopes of Mt Hebron, not far from the Nukheila area, where eight pieces of Syrian engineering equipment had been identified, working in two groups to the left and right of a ravine and clearly visible with high-power binoculars. David Eshel again:

 

'Tal had brought with him his prime gunner, Sgt Shalom Cohen and he decided to split his two tanks, each taking on four of the Syrian tractors. After several hours of tense waiting with the sun blinding the Syrian gunners below the working site on the slope, these opened fire with a Russian Guryanov machine-gun on a patrol along the track in the valley. Within 2 minutes Tal and Cohen destroyed seven pieces of equipment, the General firing HE shells from an M50 75 mm gun Sherman, while Cohen sent his HESH rounds from his 105 mm L/7 gun mounted on Centuriofr. One tractor Cohen missed, but the general saw it and sent another round to finish it off and the tractor skidded downhill. Fewer than ten rounds had been fired. All were bull's-eyes on the mark - the incident was over in 4 minutes. Both the Syrians and the Israelis were stunned by the brilliant performance. The Syrians did not respond. With a single precision operation the Israelis had deflated a grand strategy of the Syrians.

 

Tal had chosen an unexpected option and it had paid off.

 

Unfortunately that was not the end of the affair. The Syrians were still determined to continue with their water diversion plans and moved their work site further south, the new area being 6 km away from the nearest Israeli positions in the valley below. This time they were convinced that they could work unhindered from tank guns and that if the Israelis did intervene it would be a clear escalation, using air or artillery. However, they had reckoned without 'Talik'! He remained convinced that both the high-power French 105 mm low-pressure GIAT gun and the British L/7 105 mm were both capable of meeting the challenge. The former had been chosen for the Sherman M51 project and had already proved very effective and Tal himself was 'raring to go', as Eshel explains:

 

'Having practised long-range firing on the Negev ranges, Tal was ready. As at such ranges the targets were beyond visual range, high-power binoculars were used, manned by expert observers who would direct fire and correct ranging.'

 

However, range was not the only problem this time. The Syrians had very cleverly hidden their site with an earth embankment; all that could be seen were the earth-moving scoops, throwing their contents over the wall. Split-second timing was therefore required; aiming and firing had to coincide with the showing of the scoops. In addition, to ensure that the hits would be effective, Tal chose to use a bunker-busting HE round, with a delay fuse which would not detonate the round until it had penetrated the earth wall. It worked perfectly, forty rounds being fired in 10 minutes and two Syrian tractors destroyed, the fire being corrected by outside observers using high-power binoculars. This action took place on 13 May 1965 and intelligence photographs taken later showed that one of the rounds had penetrated the earth wall, gone through the elevated dozer blade, and then exploded in the tractor's engine, with devastating effect.

 

The last occasion in which Israeli tanks were involved came three months later, once again in the Almagor area. After the last engagement, the Syrians had moved their site 10-11 km from the Israeli positions. Surely now they would be able to work unhindered? However, they were in for another painful surprise. Gen Tal ordered a second model to be built on the Negev ranges, on which his gunners tested super-long engagements using L/7 105 mm APDS rounds - the only ones which were thought to be capable of performing effectively at such long ranges. As Col Eshel explains:

 

'At such extreme ranges the parameters which worked within the 2,000 m range would no longer apply. Here the natural laws of gravity would certainly decrease trajectory of the constant speed round travelling under stress from other parameters as well. Extra care was given to bore-sighting and the firing tests, examined by the use of a hopping helicopter, were encouraging. Once again, outside observers with their high-power binoculars would observe and correct the firing sequence.'

 

The fateful day arrived on 11 August, and two tanks, both Centurions, moved into position. Sgt Cohen was in charge of the one tasked to fire at the earth-moving equipment at 11 km range, while Gen Tal, in the second tank, would deal with a Syrian PzKpfw IV, located under cover at 1,500 m range. Their opportunity came when the Syrians opened fire on an Israeli tractor with machine-gun and mortar fire. Cohen's first round (at 11 km) scored a direct hit on one of the Syrian tractors. It took some time for this hit to be confirmed by the observers, but it was definitely a clear shot on the mark. By then the Syrians had reacted as David Eshel explains:

 

'Gen Tal saw that the Syrian tank was preparing to enter into the fight. He aimed and fired two consecutive rounds and the Syrian Panzer exploded into a searing flame. At this moment, the tank commander, Lt Col Binyamin Oshri, who commanded the Centurion battalion, shouted over the tank intercommunication system that he identified a Syrian T-34 coming downhill at great speed. Tal also saw it and aimed at an estimated 3,000 m range. The first round fell short, but a second followed, the tank running directly in a straight forward line so that the second round slammed home. The tank exploded, still in motion, as parts fell off the burning hulk; a fiery ball of flame rolling downhill -an extraordinary sight.'

 

At that very moment, Tal's Centurion was hit by a Syrian SU-100, which had been hiding behind a protective earth wall.

 

Col Oshri was wounded and fell onto the general who was in the gunner's seat. An APHE round had hit the commander's cupola, causing a severe shock wave to pass through the, tank, which subsequently affected the entire crew who suffered painful after-effects for some three weeks, although none of them (except for Oshri) were wounded. Oshri was swiftly evacuated and his life saved, although he was never able to return to active duty. The Syrians again moved their site to a new location east of the Sea of Galilee, some 22 km away from the nearest Israeli positions, where a high ridge prevented any further intervention by tanks. A final attack was therefore launched by the air force which destroyed the site, while the occupation of the Golan Heights in the Six-Day War of 1967 finally put paid to any further Syrian attempts to divert the vital water sources. The Israeli Armoured Corps had undoubtedly revolutionized long-range tank gunnery and had shown that their tanks could be used in a strategic role. Also it was clear that Israeli tank gunners were capable of precision gunnery of the very highest order, despite many of them being young, short-term national servicemen or reservists.

[DKTanker]

I had referred to this earlier.  This story has been repeated in various forms in several books. The presentation is typically slightly different between various authors – creative license I suppose – but the gist remains the same.  I would imagine various folks can easily find faults with some aspects of Forty’s technical presentation, however the end result is still tanks destroying point targets at extreme ranges with what appears to have been fairly low ammunition expenditures.  So what is going on here?  What’s the trick?  Dispersion tells us ammunition expenditures required to secure direct hits should be fairly high for these sorts of shoots?

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The only impressive shoot was the 11Km shot and at that I'm left with the impression that the IDF thought the first round hit was luck.

 

Hitting a 60cmx120cm target at 800 meters, not overly impressive. When zeroing at 1200 meters, after correcting for the three round shot group, most tanks would hit well within a 60cm dia circle with M724. Even HEP/HESH at 800 meters is pretty damn accurate.

 

40 rounds to hit two tractors....law of averages. Moreover, they were HESH rounds so even near misses could have target effect on unarmored vehicles. Not overly impressive.

 

I have to say this is the first time I've seen an in depth description of the events, I really wish I hadn't. I've been believing that the IDF gunners had ubermench abilities....turns out they're rather mortal.

Edited June 4, 2006 by DKTanker

[jwduquette1]

The only impressive shoot was the 11Km shot and at that I'm left with the impression that the IDF thought the first round hit was luck. 

 

Hitting a 60cmx120cm target at 800 meters, not overly impressive.  When zeroing at 1200 meters, after correcting for the three round shot group, most tanks would hit well within a 60cm dia circle with M724.  Even HEP/HESH at 800 meters is pretty damn accurate.

 

40 rounds to hit two tractors....law of averages.  Moreover, they were HESH rounds so even near misses could have target effect on unarmored vehicles.  Not overly impressive.

 

I have to say this is the first time I've seen an in depth description of the events, I really wish I hadn't.  I've been believing that the IDF gunners had ubermench abilities....turns out they're rather mortal.

328733[/snapback]

 

I think the Syrians were progressively moving their efforts further and further away from Israelis positions. The Syrians were trying to divert the flow of a canal or river. (A tangent comment, but I would think there would be a large number of topographically related constraints on where the canal alignment could realistically be moved -- however I am unfamiliar with the terrain so I will assume the Syrian civil engineers had a clue.) Anyway the initial shooting is amongst the more normal ranges -- less than 2Km.

 

Then there is a series of 6km shoots described -- which I take to be the 40-rounds required for effect. I missed that bit first time through. But this seems like a guy could justify these sorts of expenditures with normal shot dispersion theory. I suppose it doesn’t hurt to point out they were using outside observers – probably from multiple locations so that they could better triangulate range and deflection corrections.

 

Than the last set of shoots was at 10 to 11Km. 1st round hit. Ok -- I'll buy that the text sort of implies luck.

 

Just an aside, but the L7A1 HESH FTs don't extend to ranges of 11Km. They cut off around 3Km -- although the photocopied set I have may not be complete. Moreover I have the US Army A3 FTs for the M68, and the HEP tables cut off at 9.7Km. The super-elevation is indicated as 681.3-mils for a horizontal range of 9.7Km. That's about 38.3-degrees. I assume they were shooting uphill -- at least that's the way it sounds from the account. So throw in angle of site plus complementary angle of site for these sorts of ranges and you’re probably pushing shooting elevations well in excess of 40 or 45-degrees. What's the max elevation possible for a Centurion's main gun – 105mm L7? I’d guess that they would have had to construct special inclined ramps to conduct these sorts of shoots. Another reason angle of site cant simply be ignored in that these ramps would have had to have been constructed before hand and allowed for additional elevation required.

[DKTanker]

Than the last set of shoots was at 10 to 11Km.  1st round hit.  Ok -- I'll buy that the text sort of implies luck.

 

Just an aside, but the L7A1 HESH FTs don't extend to ranges of 11Km.  They cut off around 3Km -- although the photocopied set I have may not be complete.  Moreover I have the US Army A3 FTs for the M68, and the HEP tables cut off at 9.7Km.  The super-elevation is indicated as 681.3-mils for a horizontal range of 9.7Km.  That's about 38.3-degrees.  I assume they were shooting uphill -- at least that's the way it sounds from the account.  So throw in angle of site plus complementary angle of site for these sorts of ranges and you’re probably pushing shooting elevations well in excess of 40 or 45-degrees. What's the max elevation possible for a Centurion's main gun – 105mm L7?  I’d guess that they would have had to construct special inclined ramps to conduct these sorts of shoots.  Another reason angle of site cant simply be ignored in that these ramps would have had to have been constructed before hand and allowed for additional elevation required.

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The text states that APDS was used for the 10-11k gunnery.

[jwduquette1]

So much for my reading comprehension test... Edited June 4, 2006 by jwduquette1

[jwduquette1]

There's a table at the tail end of the FTs for M392 APDS for establishing range and max ordinate. Not sure of its purpose. But it gives non-typical ranges and superelevations. For 5-degrees -- about 88.89-mils -- it says range is 14950-meters. For 10-degrees -- about 177.8-mils -- it says range is 19579-meters. This goes all the way up to 57-degrees where the range is indicated as a whoopin' 45.7Km. A bit of interpolation gives a superelevation of about 59-mils for a horizontal range of 11Km.

 

I'm thinking this would easily be within the field of view of the M-105D telescope even after the correct superelevation were input. I suppose one question is would the gunner be able see the target even if it was in his telescopes field of vision? Course this was a Centurion -- but if it were an M48A5 or M60. The 20-pdr Centurion used a non-ballistic reticle and range was input by a hand knob and range drum thingie. Dunno' the arrangement for the up-gunned 105mm L7. Did it continue with a range drum and non-ballistic reticle or did they switch to a ballistic reticle? Either way, I would reckon they would have used a gunner’s quadrant to make sure they were applying the correct superelevation for an 11Km range.

 

I also don’t know if Centurions were setup with an azimuth indicator or quadrant elevation at the gunner’s position. How would you do aim off to account for spin induced drift – or cross wind if it didnt have an azimuth indicator? Spin drift is probably gonna’ be about a 0.7-mils or 0.8-mils correction at 11Km. That’s about a 25-feet to 28-feet lateral difference at that range from where you’re aiming and where you’re hitting.

Edited June 4, 2006 by jwduquette1

[DB]

I have quoted in the past from another of Forty's books about this incident. It's clear that considerable setting up effort was expended to improve the likelihood of hits.

 

I think that there are two main considerations - the first was that the Syrians were behaving predictably, following an identical route which as a consequence meant that the target range could be adequately surveyed in.

 

Secondly, a practice range was set up to establish simialr conditions for the shoot.

 

I would imagine that carefully prepared rounds were made up, too - no dings in the round, for example.

 

The way Forty tells the story is that the initial attempts to attack the positions were embarrassingly bad - it was the improvement that was impressive.

 

Based on the ranges you quote for high elevations, I expect it's about time someone posted that USMC orbit insertion attempt picture again (HEAT elevation for a Training APDS-T round at night, IIRC)

 

David

[nigelfe]

Confrontation, not communists just the regular forces of Indonesia. However, there was considerable restraint and all cross border (by UK, etc forces) was highly classified. One VC was awarded during the campaign.

 

Actually where I was shooting was the end of an airfield, about a year earlier, before I got there, the Indonesian AA gunners managed to shoot down one of their own C-130s, full of RPKAD (Indonesian SF). However, they also had Soviet eqpt (their marines were almost entirely Sov equipped), one of the most impressive aircraft noises I've ever heard was a Hook (MI 6 IIRC) heavy lift helicopter.

 

The binos were definitely not standard issue, may have originally been German coast artillery.

 

Also the scene of one of the great radio 'conversations' in 1966. Freak atmospheric conditions meant we picked up a US net across the other side of the S China Sea, we were using VHF for once. US signaller 'get off this means, this is operational', Brit signaller (gnr = pte), off his own bat 'so's this and we're winning ours', which just goes to show that the average Brit squaddy is smarter than the average US general

Edited June 5, 2006 by nigelfe

[jwduquette1]

I have quoted in the past from another of Forty's books about this incident. It's clear that considerable setting up effort was expended to improve the likelihood of hits.

 

I think that there are two main considerations - the first was that the Syrians were behaving predictably, following an identical route which as a consequence meant that the target range could be adequately surveyed in.

 

Secondly, a practice range was set up to establish simialr conditions for the shoot.

 

I would imagine that carefully prepared rounds were made up, too - no dings in the round, for example.

 

The way Forty tells the story is that the initial attempts to attack the positions were embarrassingly bad - it was the improvement that was impressive.

 

Based on the ranges you quote for high elevations, I expect it's about time someone posted that USMC orbit insertion attempt picture again (HEAT elevation for a Training APDS-T round at night, IIRC)

 

David

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This story is repeated often enough on forums it seemed a good idea to look at it in a bit more depth. It does read like a laboratory experiment. It’s also detailed in the early chapters of “The tanks of Tammuz”.

[jwduquette1]

I was looking at dispersion zones for 105mm L28A1 APDS. The 90% Zones is a uniform 0.6-mils out to the end of the firing tables – vertical and horizontal. Last range entry is 3500m. So 1σ is about 0.182-mils. Cone shaped dispersion starting at the muzzle.

 

The Syrians would have been moving a huge amount of dirt if they were serious about water diversion. I’d reckon the equipment would have been pretty large – like D-9’s or D-10 dozers and big assed scrapers (or some non-CAT machine of roughly equivalent size). The Frontal target aspect of a D-10 is about 3.5m or 4m high (excluding the cab stick-up) by about 3.5 to 4m wide excluding the excess blade width out to the side of the tracks. The side aspect presents a target that’s about 5m long – excluding the riper on the ass end of the machine.

 

A scraper is about the same in the front as a D-10, but the side aspect is pretty bloody long what with the paddles and can. These are about 12 to 15 meters long. Course back than the cans were often being pulled by a big assed dozer.

 

Running with L28A1 dispersion figure of 1σ = 0.2-mils @ 11Km (in both the vertical and horizontal directions), the hit probability against a D-10 sized bulldozer:

 

For a frontal shot on a stationary D-10 dozer @ 11Km:

Width x Height = 3.5m x 3.5m, hit probability = 33%

Width x Height = 4m x 4m, hit probability = 41%

 

For a side shot on a stationary D-10 dozer @ 11Km:

Width x Height = 5m x 3.5m, hit probability = 43%

Width x Height = 5m x 4m, hit probability = 47%

 

For a scraper side shot:

Width x Height = 12m x 3.5m, hit probability = 58%

Width x Height = 15m x 4m, hit probability = 64%

 

These are based solely upon shot to shot spread, and don’t include range estimation errors, drift errors, wind, blah blah blah. But all of these can be determined with good accuracy in a labratory setting ala the Israelis shoots described in the above account.

 

The hit probability using HESH for the above range:

Width x Height = 4m x 4m, hit probability = 1.3%

Width x Height = 15m x 4m, hit probability = 4.8%

 

Course the descent angle is steep enough that this calc should be re-run in the horizontal plane. This I think would increase hit probability slightly since the effective target footprint will be larger as a function of the angle of fall of the projectile. Unfortunately I don't have the length of the 90% Zone (Or PE or even 50% info) for 105mm HESH or HEP.

 

HESH\HEP dispersion (in mils) is not uniform with range like APDS. The 90% Zone is about 0.6-mils at 500m, but is about 1.43-mils at 3000m. So the dispersion pattern is trumpet shaped rather than conical.

 

Edited June 5, 2006 by jwduquette1