John D Salt

Curse you, JasonC, every time somebody says something ugly and Logistical like this, a Tactics Fairy dies! All the best, John.

More oomph from the propellant. According to Hunnicut (again), the Stuart's gun develops a chamber pressure of 50,000 p.s.i., the automatic gun a mere 36,000 p.s.i. All the best, John.

Well, that's an easy one -- they're different guns. The data that follow are stolen from R P Hunnicutt's "Half-Track: A History of American Semi-Tracked Vehicles" (Presidio, Novato, CA, 2001). The gun in the M15 and M15A1 is the 37mm Automatic Gun M1A2, which fires the M59A1 APC-T shot. The Stuart's gun is the 37mm Gun M5 or M6, which is essentially the same as the ground-mounted M3, and fires the M51 APCBC-T shell or M74 AP-T shot. Projectile weights, muzzle velocities and muzzle energies are as follows: M59A1________1.91lb____2050 ft/sec____63 ft-tons M51 or M74___1.92lb____2900 ft/sec____112 ft-tons As you can see, the Stuart's gun has almost twice the muzzle energy of the automatic gun, so it's no surprise it penetrates better. All the best, John.

Unfortunately that source (and the earlier WW2 FactFile by the same authors, which gives the same numbers) fails to specify the angle or plate type used, so the comparison isn't worth much. The most trustworthy estimates I have seen of the French 47mm gun's performance are from Jentz' "Panzertruppen" vol. 2 1996, which says that Wa Preuf tests indicated a performance mildly inferior to the Soviet 45mm (39mm at 100m, 33mm at 500m, 26mm at 1000m and 20mm at 1500m, agaisnt plate sloped at 30 degrees). Comparison of the APHE and APCR projectiles for the German Pak 36, 38 and 40 and the Soviet 45mm, 57mm and 76mm guns shows that APCR has a mass between 43% and 59% that of the corresponding APHE round, and a muzzle velocity between 18% and 47% higher. This seems to me to indicate that the mass and velocity figures quoted for the French 45mm cannot refer to an APCR shot -- it's far too heavy, and far too slow. All the best, John.

That's because it's one of those things you're just supposed to know, so it doesn't need writing down. How anyone is supposed to know it when it is never written down, I don't know, but I expect that that is also one of those things you are just supposed to know. I've no idea what weirdness the US Army indluges in, but the current UK weirdness I established to my own satisfaction recently, and I doubt it was any different in WW2. Assault pioneers. Some years the British Army thinks it should have an assault pioneer platoon in every infantry battalion. This year, it even thinks it should have one in the establishment without having to steal a platoon from one of the rifle companies. Next year, who knows? The equivalent of the infantry's assault pioneer platoons are the support troops of reconnaissance and armoured car regiments, who are called "assault troopers", not "assault pioneers". Royal Engineers, RE, engineers, Sappers, or in the old days of radio brevity codes, Holdfast. The RE themselves now distinguish between close support engineering (support to units) and general support engineering (support to formations), but I don't think they made such a distinction in WW2, when the divisional engineer regiment/battalion would have a number of field companies/squadrons to do the donkey work and a field park company/squadron to provide the stores and plant. Likewise, there is currently a distinction between assault bridging and logistic bridging, which I imagine must have existed in WW2. In WW2 there were also Assault Regiments RE, who would do combat engineering from under armour, using AVREs. The other funnies (Crocodiles, flails, Buffaloes) were specialist RAC troops from 79th Armoured Division rather than engineers, despite doing engineery-type tasks. The RE also have, and had, responsibility for a bewildering array of technical tasks, including ferrying, watermanship, clearance diving, railway operation, water supply, bulk petrol handling, explosive ordnance disposal, and Lord knows what else, including until quite recently the Army's postal service. This probably explains why a fairly common way for the British Army to grow a new arm of service is to hive off a specialist branch of the Royal Engineers, as it did for example with the Royal Flying Corps and the Royal Corps of Signals. The Royal Engineers do combat and general engineering with equal enthusiasm and competence. The Pioneer Corps ("the chunkies") exists to provide skilled labour for construction tasks which should, in a tidy battle, not be near the front line (although they have basic infantry skills). So, to sum up: Royal Engineers can do anything; Assault pioneers (infantry) and assault troopers (HCav/RAC/recce corps) can do some engineer tasks at the sharp end; Pioneers can do construction tasks in the rear. Yes please. Although I've already seen the film "Pionere voran!". All the best, John.

Close recce, by which I mean recce at unit level, was carried out by tracked vehicles, mostly -- the carrier platoon in the infantry battalion, and the recce troop (typically mounted in turretless Honeys in NWE 1944) in an armoured regiment. Formation recce for a division was provided by a specialist unit. In the case of an infantry division, this would be a regiment (battalion before the June 1942 nomenclature change) of the Reconnaissance Corps, mounted in a mixture of Light Recce Cars and carriers, and including mortar and anti-tank gun platoons. In the case of an armoured division, this would be an armoured reconaissance regiment, which in NWE 1944 would probably be mounted in Cromwells. The kind of recce vehicles you seem to have in mind do not really come in until we reach higher formation, whose recce needs were provided by armoured car regiments RAC. These are supposed to operate to a considerable depth, so while "recce by stealth" is the guiding principle, each squadron has, as Andreas has indicated (and using NWE 1944 orgs again) a heavy (75mm) troop for making decent-sized bangs and a support (assault) troop for dismounted work and simple assault pioneer tasks. I believe that the basic tactics have not changed much from that day to this. Movement is conducted in one of three colour-coded states, red, amber and green, according to the likelihood of contact, with red being the most cautious. Cars (they aresstill called "cars" in the British Army, even when tracked) tend to operate in pairs, bounding or stepping up according to the possibilities of the terrain. While one car watches and covers, the other will move at top speed to the next piece of cover, slowing just before it reaches it to creep in. Dismounting to reconnoitre is quite common. Moving along defined routes, the evolutions "snake" and "herringbone" are still used now and I think have WW2 origins. In a patrol snake, the last vehicle bounds to the head of the column, and as soon as it has halted the new last vehicle bounds to the head of the column, and so on forever. In herringbone, as the name implies, vehicles drive into fire positions on alternate sides of the road. All this leaves out "Phantom", the GHQ Liaison Regiment, who were part of the RAC but classified as special forces. They reported direct to Army Group, and I think their function was (as the "liaison" designation implies) largely to keep the high command in the picture without having to wait for reports to filter up from the sharp end -- as Martin van Creveld would put it, to provide the high commander with a "directed telescope". All the best, John.

Close recce, by which I mean recce at unit level, was carried out by tracked vehicles, mostly -- the carrier platoon in the infantry battalion, and the recce troop (typically mounted in turretless Honeys in NWE 1944) in an armoured regiment. Formation recce for a division was provided by a specialist unit. In the case of an infantry division, this would be a regiment (battalion before the June 1942 nomenclature change) of the Reconnaissance Corps, mounted in a mixture of Light Recce Cars and carriers, and including mortar and anti-tank gun platoons. In the case of an armoured division, this would be an armoured reconaissance regiment, which in NWE 1944 would probably be mounted in Cromwells. The kind of recce vehicles you seem to have in mind do not really come in until we reach higher formation, whose recce needs were provided by armoured car regiments RAC. These are supposed to operate to a considerable depth, so while "recce by stealth" is the guiding principle, each squadron has, as Andreas has indicated (and using NWE 1944 orgs again) a heavy (75mm) troop for making decent-sized bangs and a support (assault) troop for dismounted work and simple assault pioneer tasks. I believe that the basic tactics have not changed much from that day to this. Movement is conducted in one of three colour-coded states, red, amber and green, according to the likelihood of contact, with red being the most cautious. Cars (they aresstill called "cars" in the British Army, even when tracked) tend to operate in pairs, bounding or stepping up according to the possibilities of the terrain. While one car watches and covers, the other will move at top speed to the next piece of cover, slowing just before it reaches it to creep in. Dismounting to reconnoitre is quite common. Moving along defined routes, the evolutions "snake" and "herringbone" are still used now and I think have WW2 origins. In a patrol snake, the last vehicle bounds to the head of the column, and as soon as it has halted the new last vehicle bounds to the head of the column, and so on forever. In herringbone, as the name implies, vehicles drive into fire positions on alternate sides of the road. All this leaves out "Phantom", the GHQ Liaison Regiment, who were part of the RAC but classified as special forces. They reported direct to Army Group, and I think their function was (as the "liaison" designation implies) largely to keep the high command in the picture without having to wait for reports to filter up from the sharp end -- as Martin van Creveld would put it, to provide the high commander with a "directed telescope". All the best, John.

Tungsten rounds? Where did you get that from? I can find an SL page that seems to imagine the 47mm used APCR, but it doesn't give a source for this belief. I would be very surprised indeed the French had APCR in 1940. I've never heard it suggested before. All the best, John.

Can't help with any of those, I'm afraid, but http://www.dtic.mil/ndia/smallarms/Oxlade.pdf gives a reasonable picture of what ITDU thought a reasonable section load was before the British Army once again adopted a proper LMG. The number of rounds he suggests is: 960 rds for each LSW: 9 x 30 mag, 3 x 30 mag from rfn, 4 x 150 bandolier 150 rds for each IW: Total of 150 rds: 5 x 30 mag (also carries 1 x 30 mag and 1 x 150 bandolier for LSW) Total rds in fireteam 1410 (27 mags, 4 bandoliers) Total rds in section 2820 (54 mags, 8 bandoliers) This gives about twice the total rounds in an 8-man section as we would have had in the old days with 7.62mm NATO, as suggested by my old copy of 1 WR SOPs: 750 rds for the GPMG: 12 x 50 belt on gun, 3 x 50 belt on rfn. 80 rds for each SLR: 4 x 20 mag 90 rds for each SMG: 3 x 30 mag Total rds in section 1320 (3 SMG mags, 24 SLR mags, 15 belts). Of course any number of variations are possible, but something like 750 to 1000 rounds per LMG (or bipod-mounted rifle masquerading as an LMG) seems a fairly constant figure -- WO 32/10400, "Re-organization of the infantry battalion" recommends carrying 1000 rounds per Bren, 50 per rifle, 160 per Sten. I've not heard of "bombing up" in action, but 20+ years ago it was a SOI in some battalions to push a bergen full of ammo from platoon HQ to the fire section immediately on contact, and the basic business of infantry fighting hasn't changed much since then, so I imagine the switched-on platoons still do it. All the best, John.

Half a dozen to a dozen or more. All the best, John.

What information would that be? All the best, John.

"Never ask a man if he comes from Yorkshire. If he does, you'll know in five minutes, and if he doesn't, there's no need to embarrass the poor man." All the best, John.

I'm not sure what you mean by "not being clever enough to develop a really good AP round in useful quantities". The Soviets developed HEAT, APCR, and blunt-nosed AP rounds which AFAIK bear comparison with any contemporary design, and AIUI the USSR was not short of tungsten the way Germany was. They didn't develop APCNR or APDS, but neither did anyone else but Britain and Germany (and German APDS didn't use a tungsten-carbide penetrator, so isn't up to much). I don't think there's anything wrong with the Soviet 57mm, 85mm and 100mm as AP rounds, and the other gun armaments available strike me as sensible choices given the need for HE effect. All the best, John.

I'm not sure how drinking a case of wine would help my undesrtanding of adiabatic shear stress. But I'm prepared to give it a go. For SCIENCE. http://www.weebls-stuff.com/toons/science/ All the best, John.

Nope -- I'm trying to understand more about the mechanisms of projectile shatter, and I understand that adiabatic shear stress is the mechanism that causes shatter. The background to this is that I have a program (currently in Java, I need to re-write in Python) that implements one of Dehn's penetration formulae (from Technical Report BRL-TR-2770, "A Unified Theory of Penetration", James T. Dehn, December 1986). Dehn's formulae seem to me to be nicer than the others I have met to date, but is not generalised to account for angle of strike (which I can fix with armour basis curves), nose shape and piercing caps (which I don't know what to do about) and projectile shatter (which is why I need to look at adiabatic shear stress). Dehn's formula is generlaised to cover the case of eroding projectiles, but as I'm interested in WW2-era weapons that isn't really relevant to me. All the best, John.

I suspect that CM overstates the difference in behind-armour effect between AP shot and AP shell. The decision not to use APHE in the 2-pounder was a result of firing trials that showed no benefit for the APHE round over AP; and the Russians later filled in the HE cavity in the 45mm BR-240 round to produce the BR-240SP (SP = "Sploshniy", solid) for improved penetration. All the best, John.

On the best armour penetration figures I can find for both guns, I would think that the penetrating power of both 37mm and 2-pdr APCBC was about the same. The 37mm looks to be about the same as plain 2-pdr AP at close range, and slightly inferior to AP HV, but because of the ballistic cap it retains velocity and hence penetration better at longer ranges. Capped shot was not available for the 2-pounder until May or September 1942 (depending which source you believe), and given the disadvantage of uncapped shot against face-hardened plate, this may have made a considerable difference. All the best, John.

Excellent! Very many thanks. All the best, John.

Indeed so. Serves me right for looking at the nearest thing to hand instead of digging out a table of standard normal variates. I am now slightly mystified as to why the figure 0.74 is given in PRO doc WO 291/1330, "The probability of hitting targets with artillery fire", but I s'pose a simple typo from not hitting the "6" key hard enough would be one explanation. And the tube, surely? I imagine that it includes errors due to barrel whip and muzzle brake interference? It's not clear to me whether it includes jump -- since gun barrels tend to have pretty good rotational symmetry I can't imagine another reason for differences in horizontal and vertical dispersion, but, as you can probably tell, it's not really my subject. I suppose I should say "s.d. of projectile dispersion at the muzzle from all causes except range estimation error and laying error in tracking a moving target", but that's a bit of a mouthful. I determined this number through the long-established method of SWAG. I have a very limited quantity of gun accuracy data, so any pointers you can give to more would be most welcome. I'm not saying they're too small; I'm just impressed by how small they are. I suspect that ballistic dispersion makes a much smaller contribution to the error budget than I had previously thought. And 6, yes. I have browsed through the reports from the original studies on which exercise 5 was based, but I seem to have put the reference down somewhere very safe. All the best, John.

I was just going by the date of introduction in the Wikipedia article and Vasily Fofanov's site at http://armor.kiev.ua/fofanov/Tanks/ ...which, I notice, gives a 0.25 mil figure for "maximum dispersion" of 125mm fin rounds. I don't pretend to understand where he got 1962 from -- elesewhere onm the site he gives the date of introduction of the 125mm gun on the T-64A as 1969. Unfortunately that doesn't seem to be held at the PRO. Indeed if the catalogie is to be trusted, their collection of such stuff appears pretty thin. Maybe I should pottle over to Bovington and ransack their library... Yup. Although as this is the only source of error I'm considering apart from range estimation and laying error due to target motion, it could be held to include all sorts of things in the error budget apart from the ballistic characteristics of the gun, such as sight collimation error, trunnion tilt and so on. Sorry, I should have made this clear, I mean the standard deviation. I am using the method of calculating P(hit) described in "Applied operations research: Examples from defence assessment", by R W Shephard, D A Hartley, P J Haysman, L Thorpe & M R Bathe, Plenum Press, 1988. I understand that the rule of thumb to get from 50% zones to s.d.s is to multiply by 0.74, so the errors apparently applicable for the 105mm L7 strike me as very small indeed. All the best, John.

What do you think is wrong with the procedure you believe is used in CM? Calculating separate hit probabilities for turret and hull works fine if one assumes that the point of aim is at the join of hull and turret. If we assume that each is about the same size (not right, but close enough), then the probability of a turret hit will be at a maximum of 50% when the overall hit probability is 100%. This is far too low for a close-range shot aimed at the centre of mass of the turret, which would presumably be the case against a hull-down target. All the best, John.

Here, have a table of calculated hit probabilities for a 75mm gun with an m.v. of 620 m/sec and a dispersion at the muzzle of 1 mil (probably reasonably representative of the US 75mm M3) firing at a target 2.5 x 2.5 metres (exposed) or 1.0 x 2.5m (hull-down) and a ranging error of 20% for the first shot, 2% for the second. Moving targets are considered to be moving across the line of sight at 15 kph. ________________200m__400m__600m__800m__1000m_1200m_1400m_1600m_1800m_2000m 1st static______100%__100%___68%___29%___13%____6%____4%____2%____1%____1% 1st moving______100%___91%___45%___14%____5%____2%____1%____-_____-_____- 1st hull-down___100%___87%___32%___12%____5%____2%____1%____-_____-_____- 2nd static______100%__100%___96%___88%___76%___53%___33%___20%___12%____8% 2nd moving______100%___91%___63%___42%___28%___16%____8%____4%____2%____1% 2nd hull-down___100%__100%___96%___81%___47%___25%___14%____8%____5%____3% Things to notice are that being hull-down produces a greater proportional reduction in P(hit) at the longer ranges, and that hull-down is better than moving to prevent first-shot hits, but less good to prevent second-shot hits. Indeed, within 600m, hull-down produces negligible benefit against second shots (hence the importance of jockeying after you've fired a couple of shots). I suspect that distortion may arise in CM because the action takes place at relatively short ranges -- shorter, I think, than were typical in NW Europe -- thus reducing the value of hull-down. Possibly, too, the relatively low per-hit lethality (lower I think than is historically accurate) in CM:AK means that a higher proportion of shots will be "second" shots, and thus relatively insensitive to hull-down, than should be the case. All the best, John.

Interesting -- is there a good published source for this? That is, of course, and extemely high degree of accuracy, and I assume due to having ESR gun barrels, muzzle reference systems and all the rest of the modern gubbins. I doubt that a Soviet 125mm of 1962 vintage could match that -- indeed, I doubt that any NATO guns of that vintage could. Still, even if we credit the 125mm with a dispersion at the muzzle of 0.2 mil, the difference between P(hit) with a rangefinder and without seems to remain pretty huge once one gets to 1000 metres -- as you'd probably expect. I've extended the steam-powered P(hit) device to 3000 metres, and get the following P(hit) figures for a projectile 44mm in diameter and 3.6Kg in mass with a 1800 m/sec m.v., against a static 2.5 x 2.5m target: With ranging error of 2 % 500m___1000m___1500m___2000m___2500m___3000m 100%___100%____100%_____96%_____67%_____39% With ranging error of 20 % 500m___1000m___1500m___2000m___2500m___3000m 100%____94%_____40%_____16%______7%______4% Even with very high velocity, flat-trajectory guns with very low muzzle dispersion, rangefinding error is critical above about a kilometre. All the best, John.

I think you are confusing APCBC with APCR. Some US 76mm APCBC suffered shatter problems because of the relative softness of its nose. I do not believe it was ever a problem with APCR (HVAP in US service), partly because tungsten carbide is just too hard. AIUI the mechanism that causes projectile shatter failure is adiabatic shear-stress banding. Because of the way tungsten carbide fails, this causes projectile erosion at high impact velocities, but not failure of the whole projectile. Moreover, projectile erosion only occurs at impact velocities higher than those generally achieved by WW2 weapons. All the best, John.

Trite, but true. However, let us be absolutely clear about this; the crimes reported on this site, as invented by James Bacque, did NOT happen. They are fabrications. Bacque is either a liar or a complete idiot, and possibly both; he has been very thoroughly discredited, and even poeple who have not themselves read his crackpot inventions should not believe them for an instant. The people posting on this site, it should be tolerably obvious from the huge list of "Zionist involvement in this" and "Zionist involvement in that", are not merely liars or fools, but specifically Nazi liars or fools. All the best, John.