rexford

That's not quite what is being computed. Instead, the computation is more along the lines of the probability of there being any ball at that particular spot in the ring. This is done by making some uniformity assumptions about the distribution, namely that it is symmetric about the axis of the shell's flight. Simplifying a bit, one then takes the number of balls and divides them by the area to figure out how many one might expect to find in that area. This method looks at the chance of any ball being in that area, but it means any in the generic sense rather than in the sense of each ball. It is done this way so that one can analyze things without getting trapped in minutiae like having to compute the chance of each one (of 900!) being at a particular place in the beaten zone. I hope this clarifies rather than muddies the ideas. </font>

The one thing about John Salt's analysis that keeps me going over the ideas is the concept that each ball has the same probability of being at any one spot in the ring. From a simplistic view, balls on the left side of the shrapnel round at the time of detonation might have a higher chance of being on the left, and vice versa. And balls at the top of the round at detonation might have a higher probability of being at the top of the ring. In other words; If the powder charge detonation within the shrapnel round produces equal pressure on the bottom of the balls, balls on the left side would have a greater chance of going left and vice versa from internal pressure. The fact that the balls spread out 10m to the left and right of the line of fire at 80m shows that there may be some pressure within the stream pushing balls away from the centerline. This stuff is not my specialty (eating and gaining weight is), and the above is based on some fanciful impressions that occurred inbetween spoonfuls of Turkey Hill French Vanilla ice cream. Corrections and suggestions welcome and invited.

"Shrapnel casing does shatter upon detonation of the base charge." It's rather obvious that the casing would shatter upon detonation, or else the balls would not do their thing. The web site stated that the casing on early shrapnel was not designed to fragment. U.S. cloverleaf diagrams for 75mm HE, a very potent round, show that with a 30' air burst and a 30 degree descent angle the fragment density is very low infront of the detonation. Most of the fragments are blown to the sides. This suggests that casing fragments along the line of fire from 76.2mm shrapnel might be insignificant at 115m range when the round detonates at 15m.

While we're bringing up the IS-2 front hull armor for possible change in a last patch, how bout 122mm AP penetration? Working from the face-hardened figure which follows from the ARTKOM equation, 122mm AP should do the following thicknesses of rolled homogeneous armor (medium hardness): 201mm at 0m 196mm at 100m 179mm at 500 168mm at 750 158mm at 1000m 141mm at 1500m 125mm at 2000m 99mm at 3000m Early combat against Panthers resulted in a 600m to 700m maximum penetration range for 122mm AP, and the penetration figures in the game just don't make it. Panther glacis resistance should equal about 173mm vertical (83mm at 55 degrees from vertical). If CMBB decreases 122mm AP penetration due to shatter concerns, I would suggest ignoring the shatter business and going with the full penetration numbers. It may be more important to allow penetrations of Panther glacis at medium range than to include shattered bounces off Tiger front armor at really close range and unusually wide impact angles. [ June 08, 2003, 06:10 PM: Message edited by: rexford ]

I thought several posters did a darn good job of spporting 100mm front hull armor on the Model 1944 IS-2 tanks. Current patch has 120mm on upper and lower front hull areas, too much! Maybe one more patch? Please? Got to have 76.2mm shrapnel, as c3k pointed out.

I'm not so sure about that. With a burst height of around 2m or so, the gravity drop will have rendered a lot of the balls ineffective, thus limiting the useful length of the cone. Some of the other diagrams seemed to indicate an area of effect of around 80 x 20 meters. </font>

3ck: The concept you described is what would occur if the muzzle was horizontal. Time would also enter into the equation and gravity would pull the balls down, but not by much compared to the ball scatter and probably could be ignored. The hit probability theory that John Salt used appears to assume that each ball has a chance to be anywhere within a ring, so if there are 300 balls in Ring A each one has a chance of being on the target area within the ring (probability is function of target area divided by area of ring). And each one has a chance of being towards the bottom of the ring and smashing into the ground. So if one half of a ring is in the ground this does not change the estimates cause balls can be anywhere within a ring. ========================================== At 115m distance from gun with 15m detonation distance, cone of scatter is 25m wide and center is 2m above ground (assuming T34 gun height is 2m). If flight path of balls is not significantly altered by gravity to 115m and it doesn't seem so (see below analysis), a standing 2m tall man at 115m would be fully within Ring A if directly on centerline. Center of cone is 2m above ground, Ring A area is 1/4th of total diameter at 115m or 6.25m across and 3.13m above or below cone center along gun aim line, which catches everything down to ground level on flat terrain. Because Ring A area is circular shaped at any given range, a standing man at 3m distance from gun aim line would be partially within Ring A and mostly in Ring B. ================================================= Flight Time Considerations (not too relevant) Assume shrapnel detonates 15m from muzzle and target is at 115m range. 626 muzzle velocity and 686 m/s initial shrapnel ball velocity. Shrapnel cone expands 1m from line of fire for every 4m range, so at 100m from gun is 25m diameter cone. Flight time to 15m detonation: .024 seconds Flight time from detonation to 115m range: 0.18 seconds Gravity drop to 115m range is negligible. -0.20m. At 315m target range with horizontal barrel flight time would be 0.81 seconds with -3.2m gravity drop. Gravity drop is small compared to scatter cone.

The following sites have some interesting info on shrapnel: http://www.army.mil/cmh-pg/faq/shrapnel.htm http://www.riv.co.nz/rnza/hist/shrap/ 1.lethal velocity for shrapnel is 137 m/s in one case (18 pdr shrapnel with 13mm lead balls) 2.WW I resulted in creation of shrapnel helmets 3.shrapnel has bigger effective area than HE (verified by comparison of shrapnel area to U.S. curves for HE ground or air burst effect) 4.shrapnel case not meant to fracture or fragment so does not add to effective pieces in air (would apply to Russian 76.2mm shrapnel if same design theory was applied) [ June 06, 2003, 10:58 PM: Message edited by: rexford ]

Using a ballistic trajectory program developed by William Jurens and Nathan Okun, I estimated the down range velocity for 76.2mm shrapnel balls fired as cannister. Assumptions are 626 m/s muzzle velocity, an added 60 m/s for shrapnel powder charge (per John Kettler's figure, which may not be 100% correct but is a start), and balls act independently of one another with little influence on aerodynamics of other balls (simplifying assumption that is not technically true). Balls are 10mm diameter with 0.011 kg weight (first run assumption). Detonation takes place 10m to 20m from gun, as per German report info. Following figures are estimated down range velocity of shrapnel balls: 0m from projectile detonation: 686 m/s 85m, 475 m/s 165m, 346 m/s 198m, 311 m/s 255m, 265 m/s 299m, 237 m/s 399m, 188 m/s While shell casing would add fragmentation, many casing fragments from air burst would be to sides (if it parallels HE air burst shape), and down range density of casing fragments at 100m might be very low. But this is just a guess.

Thanks for the CMBB posting and for sharing the web site. Velocity at range can be estimated by taking the range and flight time and using this simple equation: final velocity at range = (2 x range - flight time x muzzle velocity)/flight time The equation assumes a linear drop in velocity with time and range, which may not be too bad compared to the work involved with a more exact solution.

According to my calculations and British firing test data, 2 pdr AP would penetrate 50mm of face-hardened armor at 500m on half the hits (no side angle from firer to plate facing). Hits on front of PzKpdw III Ausf J could fail at 500 yards with a bit of a side angle, especially if they landed on the nose armor. [ June 04, 2003, 09:18 PM: Message edited by: rexford ]

The initial action of Tigers in Africa where 6 pdr ATG knocked em out includes impact angle data. The impacts on the side armor ranged from 15 degrees (measured from armor perpendicular) to 45 degrees. The slope multiplier for 15 degrees impact angle is much closer to 0 degrees than 30 degrees. The Americans, during the summer of 1944, conducted their penetration range tests against Panther tanks at 0 degree side angle, where the firing gun was lined up with the hull armor facing. Combat reports for HVAP use against Panther front hulls suggest that there was little or no side angle from firer to glacis plate on many hits. [ June 04, 2003, 07:10 AM: Message edited by: rexford ]

One of my previous posts on this thread presented the muzzle velocity for Russian 76.2mm schrapnel from field guns, which ranged from 626 m/s at normal charge to 474 m/s at reduced charge. My past post also gave into on the Mundungwucht and Gasdruck (at). I also offered to share scans of the German drawings and firing tables for Russian 76.2mm schrapnel, which can be used to determine velocity at range, length of the ground hits, etc., but no one took me up on the offer.

Jason C posted : " Rexford, are those 25 pdr and Grant figures at 30 degrees? Tactical range calculations essentially have to be, because side angle of zero just doesn't happen on the battlefield. That gives just a tiny pencil at the end of a lobe shape, not an area most shooters will be in." Jason, your statement is speculation and incorrect when it is compared to the facts and some simple calculations. You always seem to squirm out of unpleasant conclusions by twisting around the ground rules. British studies of impact angle on tanks showed that hits without side angle made up the single highest probability of any one angle, and if one is giving the safe range for frontal hits it would probably be based on zero side angle from firer to hull facing. Here's why. A 10 degree angle from PzKpfw IIIH hull facing to a 2 pdr firing on the panzer introduces a 3% increase in effective armor resistance, which is nothing major and is not going to terribly influence the penetration range. A 2 pdr AP shot loses 3% of its penetration every 35m, a 25 pdr AP round loses 3% every 75m, at 500m range to 750m range. So within a 0 to 10 degree arc from firer to hull facing, which is about one-third of the 0 to 30 degree arc, the armor resistance and penetration range is about the same as a shot with zero side angle. 33% of the hits within the 0-30 degree arc is a major portion, and that is a low estimate for 0-10 degrees since the hits are more heavily weighted towards lower angles. The maximum quoted penetration range for battlefield combat would probably be based on zero side angle or close to it. I have read MANY books where panzers in the desert moved directly towards 2 pdr guns, GUNS AGAINST TANKS is one such book that comes to mind. Your range examples support the 69mm single plate equivalent resistance of 32mm/30mm. You just don't want to admit it. ================================================== Early war 25 pdr AP was fired at 1550 feet per second, later war rounds at 1897 fps. 1942 battles probably used 1550 muzzle velocity. When I use the early war 25 pdr AP muzzle velocity I am minimizing the penetration resistance of the the face-hardened PzKpfw IIIH hull front. ================================================= I think the British use of a 30 degree side angle during their firing tests is not to estimate the typical penetration range, but to see how effective the gun is under very demanding conditions. If the Sherman 75mm APCBC never hit the Tiger 82mm side armor at less than a 30 degree angle, no penetrations would be obtained, EVER! Same for T34 hits on Tiger side armor. Lorrin [ June 03, 2003, 11:30 PM: Message edited by: rexford ]

While there are stories of poor quality ammo for 45mm ATG, I have never heard of AP or APC ammo shortages. 45mm ATG did pretty good against quite a few panzers during 1941. Since 45mm was primarily an anti-tank gun one would expect AP and APBC to get priority ahead of HE.

Great work, John! Looking over the estimates I have a few notes and things to check: A. My hit probability calculation at 100m for 900 balls results in 100% within Ring A area, 61% within Ring B area, 16% within Ring C area and 3% within Ring D area. RING A AREA at 100m 79 m^2 area, 450 balls, 0.5m^2 target, 2.86 balls within target area on average RING B AREA at 100m 238 m^2 area, 288 balls, 0.5m^2 target, 0.61 balls within target area RING C AREA at 100m 401 m^2 area, 126 balls, 0.5m^2 target, 0.16 balls within target area RING D AREA at 100m 573 m^2 area, 36 balls, 0.5m^2 target, 0.03 balls within target area 2. From a simplistic standpoint, a shot with 300 balls should have one-third the hit probability of one with 900 balls if one is comparing balls per ring against ring area and target area, and 900 ball probability is less than 100%. At 300m, the 300 ball probability is about one-third the 900 ball figure, but at closer ranges the probability for 300 balls is much higher than one-third of 900 ball estimate. Could you explain the 100m calculations within each ring for the 300 ball case. Thank you. Lorrin As a crude piecewise approximation of a normal distribution, I have taken the circle formed by a section of the cone of fire at any range to be made up of four rings. The A ring subtends 0.1 radian, and contains 50% of the balls. The B ring subtends 0.2 radian, and contains a further 32% of the balls. The C ring subtends 0.3 radian, and contains a further 14% of the balls. The D ring subtends 0.4 radian, and contains the remaining 4% of the balls. So, with 0.1 radian fan angle per ring, and a 0.5 m^2 target area, we get the following P(hit)in each ring at different ranges in metres for the representative cases of 900, 600, 300 and 100 balls. They have been calculated up to the range where the P(hit) in the A (innermost) ring drops to 0.1. Depending on the mass and shape of the ball, pellet or slug, I think loss of velocity would remove most or all of the incapacitating effect at ranges around 500m. Balls_Range__A_____B_____C_____D 900____25___1.00__1.00__0.93__0.41 900____50___1.00__0.91__0.47__0.12 900___100___0.94__0.46__0.15__0.03 900___150___0.72__0.24__0.07__0.01 900___200___0.51__0.14__0.04__0.01 900___250___0.37__0.09__0.03__0.01 900___300___0.27__0.07__0.02__0.00 900___350___0.21__0.05__0.01__0.00 900___400___0.16__0.04__0.01__0.00 900___450___0.13__0.03__0.01__0.00 900___500___0.11__0.02__0.01__0.00 900___550___0.09__0.02__0.01__0.00 Balls_Range__A_____B_____C_____D 600____25___1.00__1.00__0.82__0.30 600____50___1.00__0.81__0.35__0.08 600___100___0.85__0.33__0.10__0.02 600___150___0.57__0.17__0.05__0.01 600___200___0.38__0.10__0.03__0.01 600___250___0.26__0.06__0.02__0.00 600___300___0.19__0.04__0.01__0.00 600___350___0.14__0.03__0.01__0.00 600___400___0.11__0.03__0.01__0.00 600___450___0.09__0.02__0.01__0.00 Balls_Range__A_____B_____C_____D 300____25___1.00__0.96__0.58__0.16 300____50___0.98__0.56__0.19__0.04 300___100___0.62__0.18__0.05__0.01 300___150___0.35__0.09__0.02__0.00 300___200___0.21__0.05__0.01__0.00 300___250___0.14__0.03__0.01__0.00 300___300___0.10__0.02__0.01__0.00 Balls_Range__A_____B_____C_____D 100____25___1.00__0.67__0.25__0.06 100____50___0.72__0.24__0.07__0.01 100___100___0.27__0.07__0.02__0.00 100___150___0.13__0.03__0.01__0.00 100___200___0.08__0.02__0.00__0.00 All the best, John. </font>

Jason posted "He gives as effective ranges of the Grant's 75mm a figure of 700 yards, and for the 25 pdr with AP 600 yards. These are lower than the figures the DAK staff book gives. There are in action reports from the Gazala period that have 25 pdrs killing Panzers at 800 yards, and the DAK staff guy says 1000m was the "safety" distance they tried to stay beyond because of the 25 pdr threat." The above penetration ranges SUPPORT the conclusion that 32mm/30mm layered armor resists like a single 69mm thick face-hardened plate. ;o) Grant 75mm AP penetrates about 63mm face-hardened at 700 yards, which would allow occasional defeats of 69mm face-hardened at 10 degrees from vertical. 25 pdr AP penetrates about 72mm face-hardened at 600 yards, and 68mm face-hardened at 800 yards. So 25 pdr AP would consistently defeat 69mm FHA/10 degrees at 600 yards and occasionally pierce at 800 yards. 1000m penetration of 25 pdr AP is 60mm face-hardened, which would usually be defeated by 69mm FHA at 10 degrees. If 32mm/30mm face-hardened on PzKpfw IIIH resists like a single 69mm face-hardened plate, that would allow some 800 yard penetrations by 25 pdr AP and result in failures at 1000m after armor slope is worked in. ************************************************* ************************************************* So the penetration ranges Jason just supplied for Grant 75mm and 25 pdr AP rounds support 32mm/30mm layered armor resisting like a single 69mm face-hardened plate. ************************************************* ************************************************* Against 50mm at 10 degrees face-hardened on Ausf J, Grant 75mm AP would penetrate on half the hits at 1100m and 25 pdr AP at 1200m. Jason, please keep in mind that CMBO and CMBB present homogeneous armor penetration stats, and CMBO includes the 1944 25 pdr which fired at a higher velocity than the 1941-42 25 pdr.

Really? From Dec '41 all PzIII replacements were ausf J. Remember ausf H production had ended in april 1941. Beginning in July-august '42 the ausf L ( 5cm+2cm) were received by DAK (76 ausf L). How can ausf H been the major subtype in use with DAK in Gaza 42 when all replacments were ausf J with 5cm armour? How can the ausf H have been the major subtype in 42 when only 71 ausf H were ever issued to DAK in 41? No ausf H were issued in 42. By Jan 42, 71 ausf J were in Africa, doubling the numbers in the two Pz regts. With these sort of figuers your attempts to paint the ausf H as the main, never mind half of Panzer III subtype in Africa is problomatic to say the least. (1996 Jentz). Stop pulling "numbers" and unsupported personal beliefs out of your hat to support your arguments. You've been doing this since the infamous Sherman firefly thread. </font>

How many of the PzKpfw III used by the DAK during the Gazala battle were IIIG and how many were IIIH? Avalon Hill's TOBRUK game had all PzKpfw III as Ausf H models, which seems wildly optimistic. I don't have the data anymore, but it would also be interesting to see how many AP and how many APCBC rounds were carried by the Grant in those initial combats.

The CMBB figures for 75mm M72 AP are not face-hardened penetration data, which is what we are interested in, and the Grant gun fired at a much lower velocity than the Sherman. If a Sherman gun penetrates 83mm at 500m and 75mm at 1000m, that is the homogeneous armor penetration for 2030 fps/619 m/s muzzle velocity and APCBC ammo. The British firing test results published by the Americans show 75mm M72 AP failing on several hits at 600 yards against the front armor on PzKpfw IIIH, and then that ammo obtains a complete penetration of the driver plate at 500 yards. The 500 yard penetration is "not clean". My penetration calculations for the Grant 75mm AP have 67mm of vertical face-hardened armor at 500m. [ June 01, 2003, 08:16 PM: Message edited by: rexford ]

As mentioned in the highly edited version of my last post, the PzKpfw IIIH which was fired upon by the British had a 32mm face-hardened plate bolted onto 30mm homogeneous, according to the report. Other British information on PzKpfw III armor type indicates that the main armor on PzKpfw IIIF and IIIG was face-hardened, and PzKpfw IIIH used two face-hardened plates in a layered combo. Some material I recently read indicated that the PzKpfw IIIH was a stop gap answer to the need for improved armor on the PzKpfw III hull front, and was not going to be the ultimate response. A single 50mm plate was envisioned but it took time to convert production and it was easier, at first, to add 32mm atop production vehicles. Given the problems involved in building tanks with 32mm/30mm front and rear hull armor, and in converting PzKpfw IIIG (only 1/3 could be successfully converted), 50mm plates might have been simpler from a production and maintenance standpoint. If the British firing tests were conducted at 30 degrees side angle, than adding 20mm to the 30mm main armor would have provided less than 50mm resistance. 30mm may have been chosen on the basis of who knows what criteria. Using a 30 degree side angle results in about 57mm effective face-hardened resistance for the 32mm/30mm combo on PzKpfw IIIH front. ============================================ British 2 pdr guns would have been recovered in France, as well as tanks with that weapon. 2 pdr AP penetrates a 57mm face-hardened plate at 250m on half the hits without a side angle, which might have been satisfactory to the panzer planners. Against a 50mm face-hardened plate angled at 10 degrees from vertical (PzKpfw IIIJ driver plate), 2 pdr AP penetration range for 50% success is limited to 500m. From a German perspective, the loss in effective resistance which changed the vulnerability from 250m to 500m penetration range against 2 pdr AP may have been acceptable (32mm/30mm to single 50mm), due to the many advantages it bestowed.

In response to Jason's post (see quotes that follow my statements): Since the firing report against PzKpfw IIIH left out the side angle I believe that they also left out many of the hits that failed to penetrate, and only mentioned the unusual partial penetrations or notable outright failures. There also was a short discussion of 75mm M72 AP failures at 600 yards, with significant damage to the main armor after the rounds pierced the outer plates. No complete penetrations at that range by 75mm M72 AP. When 75mm AP failed to completely penetrate at 600 yards it either broke up or ricocheted. The 75mm APCBC that penetrated did so with little remaining energy, which suggests that the armor resistance was very close to the penetration of the projectile. Contrary to British info on PzKpfw IIIH, the firing test report indicates that the outer 32mm plate was face-hardened and the interior main armor was homogeneous. This FHA/RHA combo is mentioned in two places, at the beginning of the test results and in the description of 75mm AP damage. I would guess that visual damage to a homogeneous plate might be different than a face-hardened plate, where the homogeneous plate would show ductile movement of armor while face-hardened armor would show a shatter effect on the surface. Changing subjects, why would they fire the 75mm APCBC at 1000 yards against PzkPfw IIIH front armor and only fire the 6 pdr AP at 500 yards against the nose armor and 600 yards against the driver plate? Weren't they curious as to whether the 6 pdr AP would penetrate the driver plate at 600 yards? I find it hard to believe they took the 6 pdr gun to 600 yards, penetrated the driver plate on PzKpfw IIIH, then took the gun to 500 yards, penetrated the nose, and then went on to another tank. Only fired two shots and they were happy with a test which resulted in partial information on the actual maximum penetration ranges? By the way Jason, I am still waiting to see the reference and exact words regarding combat reports that you had from Africa where 25 pdr guns penetrated the front armor on PzKpfw IIIH's at 1000m. I don't believe that the report from DAK that you referred to specifically mentioned PzKpfw IIIH. Can you prove me wrong? Bulloney. Projectiles generally fail against face-hardened armor by breaking up unless they stick in the armor. [ June 01, 2003, 03:54 AM: Message edited by: rexford ]

A very good find Amedeo! Here are some tidbits from the German report on Russian 76.2mm field gun schrapnel (source of German data is a 1938 Russian report on 76mm Kanone 1902/30 L40, Kenn=Nr. 120, I. Teil, Ausgabe 1938): "Nichtverfeuerte, bereita gestellte Dopp Z sind auf "K" (Transportstellung) zuruckzustellen. Zur nahverteidigung (bis 400m) konnen die schrapnells mit zunderstellung "K" (kartasch) verfeuert werden. Jn dieser stellung ergeben die zunder sprengpunkte etwa 10m bis 20m vor der mundung. Fallengelassene zunder durfen nicht auf die patrone aufgeschraubt werden. Die tragbare fallhohe ist in den russischen vorschriften nicht angegeben. deshalb vorsicht! fallenge lassene zunder und patronen mit zundern sind, wenn die fallhohe mehr als 1.20m betrug, als blindganger zu behandeln und zu sprengen." If someone could translate it would be appreciated.

Indeed -- although Napoleonic people who still talk about "Major Shrapnel's spherical case" might claim that they are both kinds of case-shot. I suspect that the confusion is somewhat assisted by the similarity between the Soviet designation letters Ш (Sh) for shrapnel (Шрапнель, Shrapnel') and Щ (Shch) for canister (Картечь, Kartech') -- quite why they use the latter letter I don't know, as it doesn't appear in the word Картечь. Things are not helped by Valeriy Potapov's curious decision to transliterate Щ as "She" on his excellent Russian Battlefield site. Then again, as far as I can see, his artillery pages ( http://www.battlefield.ru/guns/project_1.html ) do not seem to list any canister rounds. I anyone has a reference to a source giving the characteristics of the 76mm canister round, I'd be interested to know of it, Likewise I'd be interested in further information on the German canister for the 7.5cm L/24, a round I have not seen referred to outside the world of "Squad Leader" other than a fleeting reference in von Senger und Etterlin. Oh, and, while we're collecting them, can anyone think of any other canister rounds that are believed to have existed during WW2 (apart from the US 37mm ATk and 57mm RCL)? All the best, John. </font>

One of the German pages gives the following data for three different Russian Schr Patr projectiles: Muzzle Velocity, Mundungswucht, Gasdruck 626 m/s, 128.6 tm, 2320 at 476 m/s, 074.4 tm, 1880 at ========================== 618 m/s, 129.6 tm, 2320 at ========================== 624 m/s, 129.0 tm, 2320 at 474 m/s, 074.4 tm, 1880 at Higher velocity is listed as normale Ladung, lower figure as verminderte Ladung or decreased charge.