HE Fire Effectiveness

[rexford]

Currently doing some research on HE fire effectiveness against anti-tank guns, where existing system in CMBO seems to allow somewhat quick end to guns on first few shots against them.

If an ATG is dug in and spotted at 600m, a 75mm or 105mm tank weapon with a 30m long HE impact area (1% to 100% lethality probability within area) would theoretically have about an 8% chance of landing the first shot close enough to do something (25% average range estimation error on first try).

Came across British "lethal area" sizes for various guns which seem small for 1%-100%, especially for direct fire rounds striking ground at low angles and fairly high velocities (over 1600 fps).

Does anyone have definition of British "lethal area" or a source for HE blast drawings applicable to direct fire weapons.

==========================================

Recently came across an interesting site on British artillery that is aimed at a broad spectrum of users. Site name is BRITISH ARTILLERY IN WW II and was put together by Nigel Evans. Address is: http://members.tripod.com/~nigelef/index.htm

One of the neat items is a system to calculate the number of rounds needed to impact a given number of troops using area fire, which is based on the 25 pdr HE impact. Conversion factors for Russian, British, German and American artillery rounds. Different levels of impact are associated with different numbers of rounds, and terrain and target posture are considered.

There is considerable discussion of the model limitations and adjustments that need to be made for the various factors that influence artillery effectiveness.

The Russian 122mm and 152mm HE fragmentation rounds are equivalent to 2.2 and 2.8 times the 25 pdr effect, while German 105mm and 150mm HE have multiplying factors of 1.3 and 2.8.

Section on EFFECTS AND WEIGHT OF FIRE can be found at: http://members.tripod.com/~nigelef/wt_of_fire.htm

The site has many different sections which deal with artillery accuracy, communications and other aspects of the artillery issue, and may prove valuable on several different levels.

[John D Salt]

Originally posted by rexford:

Currently doing some research on HE fire effectiveness against anti-tank guns, where existing system in CMBO seems to allow somewhat quick end to guns on first few shots against them.

[snips]

Does anyone have definition of British "lethal area" or a source for HE blast drawings applicable to direct fire weapons.

I wish I could find the reference for this, but from memory, the usual defintion of "lethal area", also known by the terms "vulnerable area" or "area of effect", is the area within which 50% of targets will suffer an incapacitating hit. The targets will for trials purposes probably be 2 x 5 foot or similar-sized deal (pine) boards, penetration of which to the depth of one inch by a fragment was considered an incapacitating hit ("the Zuckermann criterion"). One needs to be careful, when looking at figures for areas of effect, to determine whether they account for terrain masking or not. Obviously, areas of effect against targets under cover will be much smaller. Most of the figures I have seen quote areas of effect in square feet, but sometimes they are given in square yards, just to confuse those of us accustomed to a rational system of units.

Considering man-sized targets, of course, considers only the effect on the gun's detachment. It seems likely that the neutralising effect of the fire will be more important than the lethal effect. There is also the possibility that the fire will destroy the gun itself. In this respect PRO document WO 291/620, "The vulnerability of guns to attack by bombs and shell", says that "A sunken or sandbagged emplacement restricts effective rounds to those actually bursting in the emplacement except where part of the recoil system is above the barrel."

WO 291/262, "Study of casualties caused by bombardment", gives some examples of 88mm guns surviving the burst of a 5.5" shell in the gun pit.

Both the above documents are referred to in my W2 weapons effectiveness file at the usual place, and it also includes some areas of effect for different weapons, mostly unfortunately indirect fire, but the 6-pdr and 75mm M3 certainly get a mention. I could e-mail you a Word version of the latest file if you like, but I don't think it includes anything new on this topic.

All the best,

John.

[Redwolf]

Some thoughts:

The foxholes in CMBO are modeled as very hasty ones. If you look at the exposure percentages in the LOS or target tool, you will see that foxholes offer more exposure than you would think they had from WW2 photoghaphs where only the barrel is sneaking above earth.

Then, like vehicles, the reason guns die in CMBO is mostly not knocked out (= equipment broken), but abadoned (= crew is fed up). CMBO seemed to have resevered crews that keep fighting afteer many casulties to high-quality units (crack/elite), the regular units we have in normal fight give up pretty soon.

The effect is that both vehicles and guns are often put out of a CMBO fight for minor crew casulties without the equipment actually destroyed.

Obviously there is a problem here when comparing real-world data where people tried to knock out a battery of 88s over the course of a day or longer to open the way for an upcoming tank attack, or on the other hand the 30-minutes fight in CMBO. A gun which is put out of a CMBO-size tactical fight by being abanonded would in real life be re-manned an hour later and would not could as dead in the narrative for the whole battle.

In addition, CMBO battle sizes dictate that units are usually very small, single guns are common, and the gun position as a whole is very vulnerable. Also, especially big AT guns would have enough range so that batteries distributed over several CMBO size battlefields could reach each other's target area, further adding to the robustness of the unit.

In any case, I would like to see stronger foxholes, especially in the open (treebursts are not good for guns either), and I would like dead guns and vehicles mostly caused by what is now named "knockout", and not by crews fleeing as often as they do now.

[Runyan99]

Originally posted by rexford:

If an ATG is dug in and spotted at 600m, a 75mm or 105mm tank weapon with a 30m long HE impact area (1% to 100% lethality probability within area) would theoretically have about an 8% chance of landing the first shot close enough to do something (25% average range estimation error on first try).

How do you arrive at the hard figure of 8% ?

[ May 28, 2002, 01:53 PM: Message edited by: Runyan99 ]

[John D Salt]

Originally posted by Runyan99:

</font><blockquote>quote:</font><hr />Originally posted by rexford:

If an ATG is dug in and spotted at 600m, a 75mm or 105mm tank weapon with a 30m long HE impact area (1% to 100% lethality probability within area) would theoretically have about an 8% chance of landing the first shot close enough to do something (25% average range estimation error on first try).

How do you arrive at the hard figure of 8% ?</font>

[John D Salt]

{I wrote}

If anyone can point me to a good source of angles of descent for WW2 anti-tank guns at different ranges, I'd be very grateful.

...or, just as good, a way of calculating them...

All the best,

John.

[ May 28, 2002, 05:02 PM: Message edited by: John D Salt ]

[rexford]

Originally posted by John D Salt:

{I wrote}

If anyone can point me to a good source of angles of descent for WW2 anti-tank guns at different ranges, I'd be very grateful.

...or, just as good, a way of calculating them...

All the best,

John.

It is good to see your posts on this site. Your review of our HE "hit" probability method is on the mark. We threw in longitudinal ground scatter due to the interaction of vertical dispersion and impact angle (range ground scatter is given on German ballistic tables we have).

We have German ballistic tables for APC, APCBC and HE that give descent angles every 100 meters out to fairly good range, plus our book, WW II BALLISTICS, calculates and presents descent angles for Russian, German, U.S. and British AP, APC, APCBC and tungsten core rounds using equations we received from Alvaro Figueiras. Descent angles every 100m out to 3000m.

I received your order for the WW II BALLISTICS book and are having a copy printed right now.

[rexford]

For the first shot by an IS-2 tank at a German 75mm anti-tank gun position, the average range estimate error would be about 25% of the range, which can also be used as the standard deviation for range errors.

At 300m, 600m and 1000m range, the IS-2 would be firing, on average, at a ground point 75mm, 150m and 250m away from the actual target location.

Ground scatter standard deviation for the 122mm HE round at the abovenoted ranges is 14m, 39m and 46m about the aim point, resulting in final first shot standard deviations of 76m, 155m and 255m.

122mm HE impact boxes for men standing in open would be:

75% casualty probability per man up to 10m in front of HE ground detonation

30% casualty probability from 10m to 19m in front of detonation point

5.5% casualty probability from 19m to 54m in front of detonation point

Applying the final standard deviations for the first shot to the above impact distances produces:

6% probability that first shot at 300m target will fall close enough to injure men in open

3% at 600m

2% at 1000m

Since the 75mm ATG gun crew may be in a dug in position shielded from fragments, and the men may be crouching, the probability that a first shot 122mm HE round will injure someone is small.

Fragment related casualties are not the entire picture, since close misses may cause the gun crew to duck or may pin them for a longer time.

If the 122mm HE round were fired at 10 infantry running in the open at 300m, the 6% probability would be applied to each man in turn.

The outer dimensions of the impact boxes are:

10m depth x 65m width for 75% average casualties against men in open

19m depth x 129m width for 30%

54m depth x 356m width for 5.5%

The above dimensions were calculated based on British 25 pdr HE area with appropriate adjustments for shell size. Many sources for HE blast area fragment densities give dimensions twice what I have used for same probability, so there is no one true figure. There were also differences in metal quality between nations

Based on ground scatter considerations and 0m range estimate error, max chance for an HE hit to potentially impact troops standing in open is:

29% at 300m

12% at 600m

10% at 1000m

To effectively silence a 75mm Pak, it appears that a group fire by IS-2 tanks would be required.

As noted above, some sources double the depth dimension I used so the above probabilities would be roughly doubled if an alternative approach is pursued, and the size of the box might be increased if Russian 122mm HE fragmentation rounds were assumed to use more effective explosives and metal than the British 25 pdr HE..

===================================================================

The ground scatter standard deviation for direct HE fire is a function of velocity, with slower moving projectiles having less ground scatter:

GROUND SCATTER STANDARD DEVIATION ALONG FIRE DIRECTION

800 m/s HE muzzle velocity (analysis of 88L56 and 122mmL46 firing tables)

14m at 300m, 39m at 600m, 50m at 1000m, 52m at 1800m

550 m/s HE muzzle velocity (German 75L48, American 75L40 super charge, 17 pdr HE)

19m at 300m, 33m at 600m, 38m at 1000m, 37m at 1800m

305 m/s HE muzzle velocity (British 95mm and 75L40)

6m at 300m, 10m at 600m, 16m at 1000m and 35m at 1800m

238 m/s HE muzzle velocity (U.S. 105mm)

Same as 305m m/s except 15m at 1000m and 22m at 1800m

The above stats for ground scatter indicate that if the range error were zero at 1000m and the depth of the HE impact box were similar to 122mm HE, the max injury probabilities for each HE muzzle velocity against a man standing in the open would be:

10% for 800 m/s

12% for 550 m/s

27% for 305 m/s

28% for 238 m/s

Low velocity direct HE fire appears to have a benefit in terms of near misses that are close enough to cause injury or death. High velocity HE fire would, however, have a higher probability of hitting a sandbag emplacement or gun on the fly, which is not included in the above calculations.

As noted above, injuries due to fragment hits are not the only source of benefit from HE blasts. Gun crews may be pinned or have their morale shaken for some time, infantry may be forced to ground or pinned so they do not fire effectively, etc.

============================================================================

British firing tests with 5.5" guns shooting 100 pound HE shells resulted in the following conclusions for indirect fire (which is more effective than direct fire in terms of lethal area dimensions) :

Against German 105mm howitzer:

700 square feet lethal area to prevent accurate fire for several hours with gun in open

100 square feet lethal area for complete destruction with gun in open

300 square foot lethal area to prevent accurate fire for several hours against 20' diameter gun pit

An 88mm gun in the open would have lethal areas of 1000 square feet for prevention of accurate fire for several hours and 100 square feet for complete destruction.

Above results were obtained from Nigel Evans.

[ June 02, 2002, 08:34 PM: Message edited by: rexford ]

[rexford]

"6% probability that first shot at 300m target will fall close enough to injure men in open

3% at 600m

2% at 1000m"

If a single man target is taken as 7 square feet, and there is a 3% probability that a round will hit the target, there is a 17% probability that an effetive fragment will pass within 5' of a man's head and be above ground level when the man is in an emplacement.

Since the effective fragment that passes within 5' of a man's head will be moving above the speed of sound, the fast moving piece may be recognized by the sound and be perceived as a close call threat which may lead to the man (or men) seeking cover.

There may be some research on how close a bullet/fragment has to be to men to be perceived as a serious enough threat to cause soldiers to go to ground and stay there awhile.

The other issue is something that S. L. A. Marshall examined, namely that individual soldiers are more likely to seek and stay in cover than crewed weapons (where peer pressure seems to keep the group fighting as a group long after individual riflemen would have hit the dirt).

So while there may be a 17% probability that a dangerous fragment would pass within 5' of an ATG crewmen's head, there is also a lower chance of that man seeking cover than a rifleman.

[ June 02, 2002, 08:44 PM: Message edited by: rexford ]

[Louie the Toad]

Aside from all of the numbers, according to Panzer Aces by Kurowski, once an AT gun is sighted, mostly from its muzzle flash, its life is equal to the time it takes a german tank crew to fire one and occasionally two shots at it.

If HE is already loaded this would be about 5 seconds. If HE is not loaded and the first shot misses, add another 15 to 20 seconds.

Several references to ammo stockpiles blowing up as a result of hits and near misses.

German crews seemed very good at spotting the enemy (in this case Russians). Enemy crews seemed very poor at hitting or penetrating German Tigers. Circa 1943

Timing is everything.... Toad

[rexford]

Originally posted by Louie the Toad:

Aside from all of the numbers, according to Panzer Aces by Kurowski, once an AT gun is sighted, mostly from its muzzle flash, its life is equal to the time it takes a german tank crew to fire one and occasionally two shots at it.

Toad

I've read many reports where Tigers and other panzers rode roughshod over field guns, so your point is well taken.

Here is a British statement from WO 291/620:

"A sunken or sandbagged emplacement restricts effective rounds to those actually bursting in the emplacement except where part of the recoil system is above the barrel."

The vulnerable area of a 5.5" 100 pound HE shell is of the order of 1000 square feet against a gun in the open, which comes from the same British report.

British report WO 291/471 indicates that a bullet passing within 9' of a person is considered dangerous (a high speed fragment might generate the same reaction). If there is a 3% direct hit probability the chance that a fragment will pass within 9' is 55%.

While there is evidence that Russian guns were eliminated quickly by panzers, the British seem to think that guns were difficult targets. Perhaps the Germans were better at emplacing the guns than the Russians in the cases we have discussed.

[Redwolf]

Originally posted by Louie the Toad:

Aside from all of the numbers, according to Panzer Aces by Kurowski, once an AT gun is sighted, mostly from its muzzle flash, its life is equal to the time it takes a german tank crew to fire one and occasionally two shots at it.

Not having read the book by now (bought it today), this is mostly eastern front, is it?

The Russians were much more likely to abandon a gun temporarily, so this description may not be comarable to a fight where the gun is actually disabled or the crew permanently routed.

[rexford]

My previous posts dealt with the probability of impacting an ATG with blast fragments from direct HE fire by IS-2 tanks. Direct hits on the fly were not addressed yet.

If the chance for a direct hit on the gun is analyzed for first shot chances, the probabilities are (aim at middle of gun):

300m, 61%

600m, 33%

800m, 22%

1000m, 16%

The above numbers are the percentage of first shots that will directly hit a 75mm PaK gun (3.5' height and 4' width). Thenumbers would also apply when a Tiger fires HE on a similar size ATG.

Roughly add the HE fragment probability with the direct hit percentage to obtain first shot success chances.

[ June 03, 2002, 06:24 AM: Message edited by: rexford ]

[rexford]

While the probability of directly hitting a 75mm PaK at 600m with 122mm HE is relatively small on the first shot, there is a 55% probability that HE fragments will pass within 3 yards of the crew heads when chance of hitting soldier in open with an effective fragment is 3%. British studies suggest that bullets passing within 3 yards of soldiers are considered dangerous threat by troops.

In addition, a good percentage of the direct fire misses will have a 122mm shell pass within 3 yards of the ATG crew as it flies over the gun position on long shots.

The bottom line seems to be that on first shots, 122mm HE stands a better chance of influencing the morale and efficiency of gun crews than knocking out the gun with a direct hit (or injuring crew with HE fragments).

[JasonC]

"panzers rode roughshod over field guns" (once they found them).

I don't think this is so incompatible with the first shot analysis as the discussion so far seems to suggest, or limited to the eastern front or the Russians. The problem seems to me to be the too-great fixation on the first shot, when range estimation error is highest.

The second and subsequent shots do not have the same hit probability, and a tank can fire 3 shells of HE in 30 seconds, typically. The overall probability of taking out - not just scaring the crew of - a towed gun with 3-4 shots is undoubtedly quite high, any way you slice it.

To fail, all 3-4 shells must neither hit the gun on the fly nor impact in the gun pit. The gun is smaller than a vehicle, but near misses work, and become much more likely on the 2nd and 3rd shots as range error pluments. Overall the hit probability is probably not appreciably smaller than for a tank.

It may be smaller on the first shot (smaller target to hit on the fly, range error still high) but it is probably higher by the third (near misses good enough and range error much lower).

If the chance of a close enough hit runs 15-25-35%, staying at 35 after that, by the time 4 rounds are fired 85% of the targets have been neutralized (.85x.75x.65x.65=.15). With 5-6 shots, even 5-10-15% hit chances will give a cumulative ~1/2 chance of a KO. If 2-3 tanks are firing at the same ATG, then 3/4 to over 9/10 of the targets will be silenced within one minute.

So even with low first round hit probabilities, you'd still expect tanks, typically operating in company strength and upward against batteries of ATGs, to rapidly deal with any ATGs they locate. There are enough shots available, that with any serious improvement in accuracy by the 3rd shot or so, no real difficulty would remain hitting the target. The real difficulty would be spotting them, not hitting them.

With bigger shells like the Russian 122mm, the area you can hit is bigger. But the ROF is lower, and so is the available ammo load. Overall that undoubtedly favors a smaller, faster firing gun. Because more of its shots are delivered more accurately, after the range estimation error has had a chance to fall. Fast shots with a chance to correct, still powerful enough to KO the gun with a close enough hit, is better.

This is intuitively convincing, because 122mm HE is overkill. It does not take such a large shell to kill the gun if it gets reasonably close. Doubling the blast but halving the ROF should not help when the main problem is accuracy (a point target), though it probably does help when the problem is hitting lots of men (an area target like infantry).

I suggest looking at the 2nd and 3rd shots and their lower range error. Forget about shell fragments passing near somebody's head, and just look at either hitting the gun outright (on the fly), or getting within half the CZ range (which should wound up to 3/4 of the crew). Remember to "back out" the direct hits from the CZ range near misses, though, to avoid double counting.

Then ask for the cumulative chance that all three rounds fail to hurt the gun. Redo for 6 rounds for an "outer bound", with the 4-6 probabilities the same as the third to keep it simple. I'll bet you get fairly low numbers for intermediate, combat ranges. More than one tank whenever necessary will quickly overwhelm the remainder.

The underlying point is that with multiple improving shots easily available militarily, there is no close connection between first round hit probability and ability to silence an ATG rapidly with direct HE. Once you spot the buggers, that is.

[Michael Emrys]

While nowhere in the same league with the Illustrious Grogs posting to this thread, I do have a couple of questions I'd like to raise.

First of all, I recall reading somewhere years ago that in planning for Kursk, the Soviets anticipated that on average each AT gun would kill 2-3 tanks before itself being killed. I don't know whether this claim is true or whether it worked out in practice that way, but it gave me something to think about.

As Jason says, the primary problem is spotting the gun (or more likely guns). As we know, AT gunners liked to set up in camouflaged positions and fire from a flank whenever possible. If firing from ambush in this way, it seems quite likely (to me at least) that in the ensuing surprise and confusion a battery of guns could wipe out a platoon of tanks before the tanks could return effective fire. The tanks would simply not in that case get that second or third ranging shot. But notice I said "could". I don't know what the average of first shot kills for the more common AT guns was, but I doubt it was all that high, especially for the 45mm and 50mm guns most commonly used after 1941.

So where does that leave us? I don't know, but I'd like to hear what the aforementioned Illustrious Grogs have, if anything, to say on the matter.

Michael

[rexford]

The fixation on first shot performance when 122mm HE is aimed at an ATG is because the ATG rate of fire can be three times as fast, or greater, than the 122mm.

If an IS-2 or ISU-122 silences an ATG on the first shot and it should not happen as often, it unbalances ATG performance and does not allow the realistic number of shots that might be expected.

I'am thinking of what might occur in CMBB, when it comes out, if 122mm HE wipes the board with ATG on first shots. And this issue is important to my own miniatures wargaming.

122mm HE should not be too effective on the first shot, so ATG have a last ditch chance to get off several shots in a frantic effort to silence the enemy gun before it ranges in.

SU 122 is another issue.

[JasonC]

To Rexford - I understand the importance of first shot because of ATG replies before the 2nd and 3rd, and I agree that is more important in the case of low ROF guns like the Soviet 122mm. My comment on first shot fixation was primarily directed at the discussion of combat reports that Germans had few difficulties silencing ATGs they managed to spot, and to suggestions this might be particular to Russians (abandoning guns easily or shallow positions or whatever). It isn't particular to Russians, it is in the nature of the case.

ATGs that are currently firing are typically outnumbered by the tanks they engage, and those tanks can afford multiple shots at them. So inability to hit on the first shot will not generally mean inability to kill the ATG. It may make it more likely that the ATG will get off several shots, I quite agree. So will difficulty locating the ATG until after several shots. I am seperating the issue "does the ATG get off several shots?" from the issue "do tanks generally fail to KO ATGs they spot?" There is no close or necessary connection between them. The answer to the first can be "yes" and the answer to the second can still be "no".

To clarify this, 2nd and 3rd shot analysis would be quite useful, factoring in lower range estimation errors. That will isolate the first round - "does the ATG get several shots?" question from the other one.

On the issue of ATG effectiveness and a hope that each would KO 2-3 tanks, it is pretty clear that they generally did not manage to do this. There aren't enough dead tanks for it to be literally true. Occasional guns might do that, mostly by happening to stay unspotted. But others would be knocked out by artillery before opening up at all, and others would lose their duels with the first targets they engaged, while many would get one and then be knocked out. The average kills per ATG is clearly 1 or less, if you look at large scale attrition in practice. Unless you want to ascribe nearly all AFV kills to ATGs alone, and practically none to other AFVs, infantry AT, aircraft and artillery, AT mines, etc.

The main thing to keep in mind is that ATGs generally face "many on few" engagements, odds against them. They are also more vunerable as a rule. Their strength is stealth, and the limited losses they take as the "few" side of such many on few engagements. 4 ATGs in a battery fire at a company or battalion of tanks. If they are spotted, the ATGs are going to be KOed. But they might easily take out 2, 4, or 6 of the tanks, depending on how easy the tanks are for them to penetrate, etc.

In the AARs, you find numerous cases of successful use of hidden PAK, with the guns never being accurately located by the targeted AFVs. Poor lighting conditions (e.g. dusk), long range, good cover (villages, woods), unexpected angles (not direct front), limited engagement times (a few rounds per gun only), can all help achieve this. At long range, the time disconnect between flash, arrival, and report of the gun can be several seconds, making it rather difficult to coordinate them into a firing location. The ATGs themselves are quite small, especially when dug in and camoed. The actual muzzle flash is typically the easiest thing to see, with dust kicked up near the muzzle the second. For either you need to be looking in just the right direction very close to the moment of firing.

The fact that overall, ATGs do not seem to have accounted for more than their own numbers, on average, seems to imply that such factors led to successful "stealth" engagements relatively rarely. They mattered most when that happened, perhaps, rather than it happening a lot. Many were undoubtedly KOed by forms of area fire without being distinctly located - unlike tanks. But the *average* result of an engagement with tanks pretty much has to be dead ATGs and only a few dead tanks to show for it, or the overall losses of the two seen in practice, on a large scale, don't make any real sense.

[John Kettler]

I agree with JasonC's comments, but would add that

American tank unit AARs clearly indicate that our tankers had fits finding Panthers firing at them, thanks to smokeless/flashless powder. I submit that the same should apply to German ATG's, provided that measures to suppress dust (watering, oiling, tarp, etc.) are in use. Pakfront tactics lead to

tank commander info overload, especially in massed ambush situations and with fire support integrated.

Often, the ATGs would have range cards prepared and inconspicuous markers set out. And we haven't even discussed their frequent use of rangefinders.

The situation for the tankers, especially Russian ones who doctrinally fight buttoned, thus taking by

modern U.S. Army reckoning a 50% effectiveness reduction, is extremely chaotic at best, worse when viewing an exploding world through often lousy vision blocks while being bounced around as the tank races forward. In many tanks, the TC will also be the gunner, yet may be trying to direct a platoon by flag signals or designate a target by radio while desperately trying to stay alive himself.

The German equivalent of this hell would be Kursk, with upwards of a regiment of dug-in, masterfully camouflaged, boresighted AT guns, with interlocking fields of fire, supported by prezeroed artillery, mortars and MGs. And mines. Lots and lots of mines.

ATGs should be more survivable than they are in CMBO, but Borg spotting is a major crimp on this, and CMBB options to fix this fundamental problem are limited. I really do hope to see smokeless/flashless powder and serious field camouflage depicted, though.

Regards,

John Kettler

[rexford]

"I really do hope to see smokeless/flashless powder and serious field camouflage depicted, though."

Good point, John.

To support my miniatures gaming, did some calculations for SU 122 against a 75mm L46 ATG in open at 600m (75% exposed ATG).

The probability of a first shot direct hit on the 75% exposed 75mm ATG by SU 122 is about 16%, with less than a 3% probability that fragments from near misses would hit each crew member. I assume SU 122 rate of fire would be about same as IS-2.

Since SU 122 is easily penetrated by 75mm L46, a scenario where two or three SU 122 are surprised, face-to-face, by a 75mm Pak at 600m could result in the ATG getting all three before they can accurately fire back.

While ATG on average may live a short life with a handful of kills per gun before the end comes, if we look at specific situations where the tank armor is poor, the tank gun velocity is low and the SPG rate of fire is pitiful compared to an ATG, then the ATG might get the upper hand if SU 122 first shot probabilities are where they probably should be.

It is critical that first shot probabilities for effective HE rounds be carefully modeled so that ATG have a chance to clear the field in some situations.

Regarding ATG in the open, the British in North Africa camouflaged ATG in the open with nets, which seems to have worked pretty good. German panzers were caught by surprise several times when the nets came off the 6 pdr ATG.

[JasonC]

To John - I agree that spotting them was the trick. Especially at ranges well above 600m, more like 1.5 km, where the time disconnect between muzzle blast, shot arrival, and report is marked. At closer ranges they are close enough together in time that spotting becomes much easier.

But it is easy to exaggerate the usefulness of ATG stealth and convince oneself it was the norm rather than an outlier. ATGs undoubtedly made the largest difference in cases where they were not spotted. But undetected successful ambush cannot have been the rule. To see this, look at overall US tank losses in the west. They are lower than overall German tank losses in the west - against US and UK. (There was a huge thread on this subject a few months ago, and the data is quite solid on that point). The Germans deployed at least as many ATGs in the west as AFVs. If the average ATG was killing multiple AFVs before dying, then Allied AFV losses would have been much higher than they actually were.

To Rexford - I like the 3 SUs against the ATG example. And certainly, low first shot accuracy makes it possible the PAK might "run the table" in that situation. But let's look at it for a second, with some numbers.

The 3% figure for each crewmember means one round has about a 1/6 chance of hitting at least one of the 6 crewmembers (1 - .97 ^ 6). (If I haven't misunderstood what that figure means). Which might well suppress the gun - one man or more will be hit and others will all have shrapnel nearby. Perhaps you'd have to hit 2 men to really suppress it. A direct hit will take out the gun, obviously. Together those are going to put the chance of a first round killing or suppressing at 20-30%, depending on how likely 1 man hit is to suppress the gun.

But there are 3 SUs. If all 3 fire with that probability, then they together have a 49-66% chance of taking out the gun. If the gun has already killed one, then the remaining 2 have a 36% to 49% chance of taking out the gun. With their first "salvo".

Suppose 2nd shots only marginally increase the chance of a direct "on the fly" hit, say to 20%. But cut the range error enough to make the fragments vs. one man figure rise to 6%. The the chance that one of the crew is hit by fragments would be 31%, and the chance that the gun is KOed by a direct hit or suppressed by fragments hitting one of the crew might be as high as 45%. Or as low as 30%, if 2 crew need to be hit. If 2 SUs are alive for their 2nd shot, then you'd expect an additional 49-70% chance of taking out or suppressing the gun. If only one is, then 30-45%, obviously.

The third shot would undoubtedly improve further. Put the kill or suppress chance at 35-50%. Suppose one SU might be alive for this, or not.

Then a 3-2-1 sequence would accumulate what chance of killing or suppressing the gun? As high as 95%. A 2-1-0 sequence would give somewhere in the range 55% to 72%. A 2-0-0 sequence would give 36% to 49%. Which of these is more likely depends on the ROF of the gun relative to the SUs, and especially on its own first round kill chances. It is certainly possible to run the table 1 on 3.

Certainly you'd get the wrong picture if the SUs were given a 50-75% chance of KOing the PAK on the first round. Then the overwhelmingly most likely outcome would be the PAK does or does not kill its first target, and then dies to the replies. Rexford is quite justified in warning against that picture of things, and thus stressing the low first shot kill probability and its effects on the duel.

But with realistic odds imbalances (tanks operating in companies and battalions, PAK operating in batteries) and anything under "certainty" for the PAK's own kill chances, the PAK is not heavily favored. The picture still fits the general comments of tankers, that spotted ATGs don't poise much of a problem, and the difficulty is spotting them. It is the "multiplied out", cumulative chances - from multiple shooters and over a couple of shots apiece if they are needed - that does the ATG in. Not the ease of placing the first HE round close to the gun. With many shooters and second shots, that just isn't necessary to get a high cumulative chance from all shots combined.

For what it is worth.