rexford

The John Salt site, at http://salts.britwar.co.uk/, has some combat hit probabilities and notes from Korea regarding first shot hit probability (look under WW 2 Weapon Hit Probability): 0-350 yards, 84% for all ammo types 351-750 yards, 63% 751-1150 yards, 39% 1151+ yards, 16% Interesting that hit probability at 350 yards and under is not closer to 100%. Another nice tidbit is that hit probability under poor visibility conditions was HIGHER than shots in good visibility, tankers stated that sunshine glare played havoc with sighting.

I have seen American infantry throw smoke grenades in war movies and in some actual footage. The actual use may be similar to Sherman 75mm gun use of smoke, the rounds were there but under the heat of battle use was forgotten or less than one would estimate based on availability. Have there been any past threads on smoke use in CMBO that would be good reading for someone doing research on smoke effectiveness in the game. I used Sherman 75mm smoke in one game to box in a Tiger II, which did not attempt to move through the smoke clouds that surrounded the tank. Eventually the Shermans ran out of smoke and had to face a Tiger II. HC smoke, which is what American tanks in CMBO use, doesn't start to work much for over a minute, which is what happened in the game we played. HC base emission smoke has a minimum effective range of 850 yards, ranges shorter than that result in too much impact damage to the round I guess. Max range is 1600 yards. ASL infantry smoke reduced the accuracy or effect of fire through or into the smoke hex, and the chance of using smoke was far from certain. A standard 4-6-7 German infantry squad has a 17% chance of using infantry smoke (which slows them down by 1 or 2 movement points, and prohibits any movement at all by a unit if they roll 6 on the placement roll with one dice). If three German infantry squads in one hex are going to run to better cover and try to cover their retreat, the chance of getting covering smoke is not too great. If those three squads get one smoke grenade to work, it adds +2 to the rolls against them, which basically negates the -2 for moving in the open. But they run slower and there is a chance they may not move at all due to the smoke placement attempt. ASL puts a maximum limit on smoke line of sight hindrance in one hex equal to +3. ASL has a balanced view of smoke that makes it potentially available but its use is iffy and has disadvantages. We never used it alot.

Wittmann knocked out several T34 at Rowno with one shot per tank, with the StuG IIIA. PzKpfw III with short 50mm gun beat out T34 in a cross country race experiment conducted by Russians. The multiple gears helped the PzKpfw III, as well as the suspension. StuG III used high magnification scissors scopes which allowed better range estimation and precise aim points. And with scissors scopes a StuG could go vehicle down and still watch for ambush victims.

I have never seen mention of a PzGr 39 round for the 7.5cm L24, but it seems to me that the striking velocity would be so low that there is no thing to be gained by having a piercing cap. I can't find a description of the 7.5cm K Gr rot Pz round, but I would think it most likely to be APHE, which was more or less the customary AP nature for low-velocity weapons. All the best, John.</font>

The 95mm HEAT round should not penetrate the Panther glacis since the armor quality factor does not apply. Some wargames have required HEAT rounds to overpenetrate a target by a certain amount to do anything major, so marginal HEAT penetrations might be less lethal and damaging.

Panther glacis resistance to HEAT equals 80mm divided by cosine (55 degrees), or 139.48mm vertical. Multiply by 0.85 quality and one is left with 119mm vertical. Since 95mm HEAT penetrates 125mm vertical, 0.85 quality Panther glacis is defeated on most hits. A hit on 80mm plate at 55 degrees vertical and 20 degrees horizontal, with 0.85 quality, resists like 126mm vertical. Since HEAT is fired at a fairly low velocity it will be coming down at an angle when it hits Panther glacis, which further decreases resistance to HEAT rounds. The issues that may render the 95mm HEAT vs Panther glacis result ahistorical and somewhat unrealistic is that only a small percentage of Panther glacis were flawed, and the flaw was not in the resistance to HEAT but in the ability to take a high velocity impact from a large knietic energy round and not crack, flake or disk. Many folks feel that the flaw factor that applies to armor piercing ammo should not apply to HEAT rounds, and that is my own opinion. And maybe 20% to 30% of Panthers had flawed glacis, not every one like CMBO appears to assume. The same issue applies to T34 armor. Against 75mm APCBC, 45mm at 430 Brinell Hardness (very hard) loses 24% of resistance due to brittle behavior. Against 75mm HEAT, the 45mm at 430 Brinell Hardness armor gains about 10% in resistance since hard armor is more difficult to melt (hardness is ability of particles to hold together and resist pulling apart in absence of a sharp and large impact). So armor can be poor against kinetic energy rounds and very good against HEAT penetration. [ July 04, 2002, 02:30 PM: Message edited by: rexford ]

Perhaps you are thinking of cannister, which is not precisely the same thing as grapeshot even if it operates on a similar principle. So far as I know, grapeshot was not used after the close of the 19th. century at the latest. Such a round was made for the 37mm. I sort of vaguely recall somebody mentioning a cannister round for the 57mm as well, but it isn't the kind of memory that I trust. Michael</font>

There was an HE shell for 6 pdr and U.S. 57mm guns. 6.2 pound projectile with 0.4 pounds explosive. U.S. T18 HE round was issued for 57mm gun early 1945. British 6 pdr HE available to U.S. 57mm in Europe June 1944. British 6 pdr HE available to British units February 1943. Nigel Evans has indicated that British did not issue HE to anti-tank guns until 1944 due to a fear that HE use would prematurely wear out the barrel. 6 pdr APDS rounds are used by U.S. 57mm ATG in limited quantities starting summer 1944.

I would appreciate hearing from players who have experience firing Sherman smoke, particularly how effective it is and any tips on use. We've been reading up on Sherman 75mm smoke rounds, and it takes one to two minutes to effectively screen a target and several tanks firing at once to do it (according to field manual). The HC smoke is limited to 850 to 1600 yards effective range, with the shorter range based on damage to projectile as it hits ground at ranges below 850 yards and the higher range limited by muzzle velocity and gun elevation. The HC smoke round is used by bouncing it in front of the intended range and having it ricochet about 100 to 300 yards before it came to stop. It would seem that the round might bounce a bit to the side of the intended flight path as it ricochets along the ground. One obvious problem is that the average range estimate on first shots is about 25% in error, so half will be long and useless when one is firing smoke. Some of the shorts will be too short to decrease the Tiger II arc of fire. I thought smoke would help protect Shermans from King Tigers over open ground, but our initial games resulted in the usual slaughter except that it took longer. Many of the smoke rounds did not seem to land very far in front of the Shermans. Thanks for helping out. [ June 22, 2002, 07:15 PM: Message edited by: rexford ]

Pershing has a curved 114mm mantlet, similar to Panther 100mm mantlet in shape except no tendency to ricochet defeated hits on top of crewmen heads or into their laps. 76mm armed Shermans do have 89mm cast mantlet that is angled at 10° or so. Actual measurements of 76mm gun mantlet show 98mm thickness in two cases as opposed to 89mm design spec. Putting a heavier gun in a tank sometimes means that the turret weight cannot be increased. When IS-1 with its 85mm gun (IS-1 turret designed to balance weight of 85mm gun) is replaced by late model IS-2 with its 122mm gun and very thick and highly sloped front hull, the turret armor cannot be increased. Panther has over 200mm effective vertical resistance against 17 pdr APCBC hits on glacis, but only 100mm cast mantlet cause weight considerations limit turret armor. I would guess that 76mm Sherman mantlets were limited by weight of turret when 76mm gun and new turret replaced 75mm gun and older turret shape. And Pershing turret armor also appears to have been limited by weight issues so resistance could not match upper hull front.

All of the 75mm armed Shermans had sloped mantlet and turret front armor. CMBO attempts to model the ballistic resistance of the turret front/mantlet as opposed to the thicknesses and angles. For a reason. The later 75mm gun mount had an 89mm cast and curved gun shield spaced behind a 51mm cast and curved rotor shield, so 140mm of curved armor on the turret front mantlet area. Now come the disadvantages, which are considerable: 1. spaced armor is not as resistant as a single plate, so 89+51 does not equal 140. 2. armor is cast so reduce resistance 3. inner 89mm shield is chock full of large openings for gun, vision devices, machine gun, etc, so reduce resistance for edge effects 4. penetrations of 51mm outer shield that fail to go completely through 89mm inner shield may result in something called "keying", where the round sticks in the outer and inner shields and prevents gun elevation changes 5. if projectile penetrates outer shield but is stopped by inner shield and the HE burster detonates, explosion is likely to mess up gun aim and other things. We did a detailed ballistic analysis of the resistance provided by 51mm/89mm shield combo against 75mm hits, which took into account edge effects, cast armor deficiency to rolled armor, spaced armor factor and impact angle. The average resistance of the combo is 89mm vertical, exactly what CMBO uses. Here are some of the breakdowns from our analysis of 51mm/89mm shield combo: 36% hit total effective resistance of 75mm vertical or less 43% strike effective resistance of 85mm or 95mm 13% hit 105mm to 125mm 8% hit 145mm to 165mm NOTE:Above results do not take "keying" into account So 79% of the impacts on Sherman 75mm gun shield area will be resisted by a single vertical plate equivalence of 95mm or less. Since CMBO does not treat the area as a complicated curved arrangement with all of the peculiarities and vulnerabilities, a single vertical 89mm plate is used, which seems reasonable for wargaming. We use the statistical breakdown in our miniatures gaming, so the Sherman shields will occasionally defeat a Panther or Tiger hit, which is likely to stick in the shields and disrupt the gun elevation or detonate and mess up the sight and machine gun. [ June 22, 2002, 07:16 AM: Message edited by: rexford ]

Michael Embrys wrote: "One reason I ask is because some projectiles use base or tail fuses. These obviously would not strike the ground (or other surface) and I always assumed that the deceleration of the projectile caused the fuse to initiate." For base or tail fuzes to work does the round have to be decelerated or will a change in direction (such as bouncing off the ground) do? Robert Livingston noted that Sherman 75mm HE had a graze fuze so impacts on shoulder or ogive would be sufficient to set round off. Low angle fire at high velocity with close to medium range ground target would result in shoulder impact. Would base or tail fuze HE detonate if it hit ground at low angle and bounced upward?

If a Sherman fires a 75mm HE shell at infantry 300m away and the projectile nose does not touch the ground as the round impacts the ground and starts to bounce, will the HE shell explode if it set for quick fuze? For ricochet fire to work with fuze set for delay, it would seem that the projectile nose would not impact the ground. The question came up when someone said that if an IS-2 fires 122mm HE fragmentation at an ATG and the round impacts flat firm ground at less than 1° impact angle, the round would not explode since it is not retarded and the nose will not impact the ground. Help on this would be appreciated. Thanks.

A T34 or KV-2 armed with HE shells is still going to overpower the armor on the PzKfw III's, IV's and 38t's that are met during 1941 battles. Given the face-hardened armor used on IIIG, HE shell hits might be even more lethal than AP or APBC due to the splintering effect when hard armor is defeated. Armor penetration figures for HE shells fired by T34 76.2mm and KV-2 152mm are up to the task against 30mm armor.

& yes, & to me, too! thank u. </font>

One other issue that retards tank ROF is fumes in the turret, which could become quite thick in some vehicles. ATG crews don't face the same problem, although they must put up with HE shells and fragments flying by their heads while they do their thing. The fumes issue is what kept the 100mm gun out of the IS-2 turret during late 1944, among other factors.

6 shots per minute is reasonable rate of fire for many weapons in combat situation, which is about 10 seconds between shots. If two targets are at about the same range and the first shot is a hit and a clear knockout punch, then the second shot/target can be taken without having to change the range setting. Time between shots would be greater for misses since revised range estimate would be needed and gun aim would be changed. Hitting a target without clear sign of knockout might result in continued firing at target. If 88mm Flak were trying for max rate of fire without caring about anything else, rate of fire would be much higher than 6 per minute. A Tiger tank can probably shoot at 6 per minute.

Pigg Dogg wrote: "In Band Of Brothers attack at Carentan, it seemed that the heavily sloped armor TD that the US zook team took out was a PzIV/70. Am I correct? That vehicle did not look like a mere, plain Jane Stg. I don't remember seeing a Jadgpanther in that episode, unless the Jadgpanther is a PzIV/70. (request Grog comment here)" The vehicle knocked out by the bazooka team looked like a StuG, it had the hull top MG and the armor seemed to have several different sloped areas like a StuG. My recollection was that a Jagdpanther was in the TV show, but I could be wrong. Would appreciate comments on that issue. In every scenario I played the Jagdpanther was immobilized by a track hit, which made it easy for Shermans to move out of the 88mm covered arc (except the last scenario where the Jagdpanther knocked out all six Shermans). In the scenario I added a Marder to, a .50 cal machine gun penetrated that 10mm "plate" that protects the crew and knocked out the "tank". Marders are definitely not assault guns, I forgot the Americans had .50 cal MG and paid the price.

We were particularly impressed with the TV show where the airborne troops are defending a tree line and the Germans attack with Stug III, Jagdpanther and their paratroopers. All is going so-so until the Shermans come to the rescue and beat back the Germans. This is the show where the paratroopers run into the open and knock out a Stug with a bazooka. We set the scenario up with terrain contours and tree lines that seemed to match the TV program, and the Shermans were later turn reinforcements (usually came on board during ninth turn). Several of the replays matched the show pretty good. The Germans used armor and infantry fire to beat back and pin the Americans, and had the U.S. para's in a box when the Shermans arrived and started blasting the German armor and para's. Like magic, American infantry rushed out of hiding and attacked under cover of 75mm Sherman HE once the Shermans gained momentum. Instead of retreating as the Americans surged forward, the Jagdpanther stood its ground, took an immobilizing track hit and was knocked out by a bazooka hit to the side. Oddly enough, the Shermans set up just outside the gun arc of the immobilized Jagdpanther and pounded the German troop positions while the panzer stood without any targets (it was out of HE and no enemy armor to shoot at with AP). In another replay, American infantry ran forward into the panzer guns, shortly after the Germans took the flag at mid battlefield, and were decimated. Elite troops would do this? The Jagdpanther charged five Shermans at under 150m but was unable to fire on any of them due to a terrain block (Shermans could be seen from a location behind the Jagdpanther but the JgPz V gun could not see them). Overall the replays usually ended up similar to the TV program, German armored surge is stopped and Shermans turn the tide. We added a Marder III to one replay and it was knocked out by machine gun fire. CMBO 75mm smoke didn't seem to do much when it was fired at the Jagdpanther. CMBO is really impressive during combined arms games and seems to agree well with TV combat results.

"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.

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.

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).

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 ]

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.

"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 ]