rexford

Please note that my morning calculation for ASL HE against dug-in ATG should have been 25% effect after a hit, and 17% hit probability, combining for 4% on first try, 7% on second and 11% on third. The chance of landing HE close enough to an ATG to do something in ASL, and then have it do something, is REALLY SMALL. Seems like one would be better off having all machine guns blazing away at once (bow, turret and turret top mounted). Against a dug-in ATG, using all three machine guns on a Sherman would break the ATG crew 17% of the time, which appears to be the best way to go about breaking the morale of an ATG crew. My computer program for the above calculations is giving me problems. The above figures are after the spreadsheet was corrected (and were checked using my hand calculator) but should still be treated as draft until I am sure all the bugs are out. Thanks. [ 12-02-2001: Message edited by: rexford ] [ 12-02-2001: Message edited by: rexford ]</p>

The aspect of ASL that gives emplaced guns a BIG advantage is that the dice roll analysis to see if they lose concealment status if they fire in enemy LOS. If a dug-in and hidden 75mm Pak fires on advancing Shermans at 300m in full view of some American units (say a small infantry recon unit sent in advance of the tank unit), there is a 67% chance the ATG will still be concealed. Concealed units can be fired on but they are more difficult to hit. We ran 12 ASL scenario's where 5 Shermans advanced on one hidden 75mm Pak, and the Shermans pulled to a halt at 300m after the initial shots were fired. On average, the ATG got 3.6 Shermans per scenario (scenario stops when all Shermans are knocked out or the gun crew is broken/gun malfunctions). In six scenario's out of twelve, the Shermans got the gun crew, or the gun malfunctioned and the crew broke morale before they fixed the gun, while suffering an average of 2.2 Shermans lost. In six scenario's the ATG got all 5 Shermans before they got the gun. The Shermans were the beneficiencies of some really good and unusually low dice rolls, so in most games the gun would get all the Shermans. Can a 75mm ATG fire from a dug-in position and still retain some fairly substantial benefits from concealment in terms of being difficult to precisely pinpoint for HE and machine gun fire? Maybe if the ATG was using smokeless and flashless ammo, but the ASL rules for concealed ATG apply in the same way to U.S., Russian, British and Italian ammo. Advantage to guns in ASL: even if they fire from a hidden emplaced position at a Sherman platoon 100m directly facing them, the gun can (regardless of smoke/flash tendencies) still retain some concealment benefits with the right dice rolls. Sounds right? My read on ASL is that concealment is lost if any good order enemy unit is in LOS and 640 meters of firing ATG and the dice roll is 5 or 6 on the colored dice. So stray infantry have the ability to instantly report the position of units to everyone. Is this correct, ASL fans? [ 12-02-2001: Message edited by: rexford ]</p>

My previous post brought out the low probability of a single Sherman knocking out a 75mm Pak with aimed HE on one shot. Shermans would get a 1-in-6 chance of a second shot per turn, and if three or four Shermans gang up on the ATG the odds become reasonable. One Sherman against one dug-in 75mm Pak in ASL is a low success situation. One Sherman with a platoon of infantry against a dug-in 75mm Pak, or five Shermans with a few squads of garand toting troopers, becomes a better scenario. I might also add that ASL bases HE punch on shell diameter, so 76mm HE and 90mm HE is more effective in ASL than Sherman 75mm HE. It is now well known that Sherman 75mm HE packed more punch per ounce than U.S. 76mm and 90mm HE (75mm HE has higher fragment density at all ranges, and very close to 105mm HE fragment density close to the 75mm explosiion), so ASL may very well underestimate 75mm HE performance. Russian 76.2mm HE packs as much or more HE filler than 85mm HE, so one might also expect 76.2mm HE to be under-rated in ASL (76.2 HE would be more effective than 85mm HE in terms of fragment density). CMBO gives Sherman 75mm HE greater effectiveness than 76mm HE, which may also account for difference in game results (I think 75mm HE should be closer to 90mm HE rating, but that is a dead horse that should not be kicked anymore).

The question is very good regarding why one ruleset makes knocking out ATG alot harder than another. Is one ruleset right and the other not so right, or is it that no one really knows the answer for sure, and both efforts are based on the designers perspective. If an unbuttoned 75mm armed Sherman during 1944 spots a dug-in 75mm Pak in Advanced Squad Leader at 300m, they can use area fire (spray HE all over the place) or try for direct placement of a round close enough to impact crew or gun in a large way. --------------------------------------------- AREA FIRE OPTION +1 to TO HIT roll due to gun size, and +2 emplacement modifier once hit. So potentially effective shot on 42% of first try shots. If the Pak crew has a morale of 8 and no leader the chance for broken or eliminated result is 11%. Area fire succeeds in doing something major on about 5% of first shot tries, with second and third shot impact chances of 6% and 8%. ----------------------------------------------- INFANTRY TARGET TYPE +3 modifier on first shot try due to emplacement and gun size, for 17% possibly effective hit probability on first heave-to. Chance for something major from first shot is 25%, for combined first shot hit and "do something" probability of 4%. One second and third shots against ATG overall impact chance climbs to 7% and 11%. ----------------------------------------------- A dug-in anti-tank gun is one tough target type in Advanced Squad Leader. Why? When one aims at a tank they are shooting for the middle of the vertical and lateral mass, and if the range estimation is a little high or low there is about the same probability of hitting. With a ground target, HE effect tends to be infront of and to the side of the explosion so if one is a little long the effect is greatly reduced. The loss of effect due to a long shot is not quite halved but close for discussion purposes. If one is shooting at a tank at 300m range and one is off in the range estimation by 100m (33% error), a hit will still occur. If one drops an HE round 100m in front of a dug-in ATG, or 100m behind the gun, the crew will probably not be impacted too much (unless their ammo reserve coincided with the HE shell hit). Even if the range estimation for an HE shot is close to actual, up-and-down random dispersion of the shot may carry the round far from the target. What HE can do against dug-in ATG is raise enough dust and earth to lower the ATG rate-of-fire or suppress the crew, while the Sherman peppers the area with explosive rounds. When visibility between ATG and tank is reduced due to exploding ground hits in between the two, the tank has the advantage. We have not done the ballistics analysis to see if a Sherman firing on a dug-in anti-tank gun at 300m would have such low impact probabilities as ASL predicts. Since lateral spread of the HE shots is bound to be small at 300m, one could increase HE accuracy by walking HE onto the target and then keep the rounds hitting in front of or to the side of the gun. A Sherman might also be able to use ricochet HE fire to negate the some of the emplacement modifier (air bursts at an altitude above the gun shield stand a better chance of hitting some gun crew members). We will do some analysis and see what a reasonable To Hit probability would be. Thanks for raising a very interesting issue. [ 12-02-2001: Message edited by: rexford ]</p>

And I forgot to add that it takes more solid shot 37mm penetrations to kill or burn a target than a Sherman's 75mm APCBC with HE burster. So expect more ammo expenditure per knocked out tank.

After I posted Jeff Duquette's 57mm ammunition information on AFV News site, Bob Smart responded with the following: "I just pulled the Ordnance Department: Procurement and Supply" Green book off my shelf. On page 152 there is a table of Ammunition Procured 1 July 1940- 31 August 1945. It states that there were 12,321,000 rounds of 57mm gun ammunition produced. Your total above adds up to 12,469,000. That is a difference of about 1% so I think they correlate pretty well. But it doesn't leave much space for any other types of 57mm rounds. If my math is right the split is 85% AP, 15% HE. Seems reasonable to me. By the way some interesting numbers in the table. There were 1,087,083,000 rounds produced of 'Major Types' ( doesn't include a few minor types such as 7.2", 6", 5.5", & 120mm). The largest amount was 411,302,000 20mm (aircraft). Second was 93,434,000 105mm Howitzer rounds. Third was 78,093,000 37mm (tank, antitank, & canister)! That number surprised me I never realized that 37mm was that important." It appears that 57mm cannister use was restricted. Funny about the 37mm ammo number, but when one considers how many Stuarts, 37mm anti-tank guns and 37mm armed armored cars were around the numbers seem reasonable. Plus 37mm armed vehicles could hold more ammo and fire it off at a much higher rate of fire than 75mm armed Shermans.

Our book, WW II BALLISTICS: Armor and Gunnery, uses the British system of projectile cap designation since it helps to explain a number of characteristics, such as rounds with a "BC" attached have lowered air resistance and carry better. Ballistic cap. I made a bigger than necessary deal out of the cap designation business because U.S. APC may be correct nomenclature if one understands U.S. nomenclature but it can cause confusion when American and British rounds are compared. I have also had people familiar with American ammo correct me when I referred to 75mm M61 as APC because the U.S. did not use APC rounds, they were APCBC according to British designations. Guess that that correction I received stuck with me for over 15 years. I'll drop the crusade.

Great effort Jeff, that clears up alot of controversies in an authoritative manner. Thanks for the hard work. Lorrin

The Russian Battlefield indicates tank and SP gun ammo types on the following site address: http://history.vif2.ru/guns/defin_4.html This data can be used with the cannister ammo designations to determine which vehicles could fire the stuff.

The Russian Battlefield site, at: http://history.vif2.ru/guns/project_1.html has data on Russian cannister shot, which was fired by 45mm, 57mm and 76.2mm guns. I didn't see anything on number and size of balls, but didn't look too long.

The Germans had cannister rounds which were much valued for their use and effectiveness against human wave assaults. The PzKpfw IVH Universe site, at: http://ourworld.compuserve.com/homepages/willphelps/Specs.htm indicates on page 3 that the 75mm L24 gun fired case shot with 960 9mm balls.

The reason I went into U.S. cap stuff was to avoid the confusion that many make when they read U.S. APC and think that it is different from APCBC. I believe that at least one poster on this thread corrected me when I said U.S. 57mm ammo was AP and APCBC, stating that they used APC. The use of APC for U.S. capped rounds leads to the sort of confusion I just indicated. To be correct and minimize confusion, the British description for U.S. rounds, APCBC, fills the bill. My intent is not hair splitting accuracy and completeness, it is a definition of the cap situation that is not confusing. The designation for solid shot and HE bursters, or tracers, do not lead to similar confusion and seem straightforward. The truncated U.S. approach has mislead many and will continue to do so, since APC and APCBC appear to be two different rounds (British 6 pdr fires AP, APC and APCBC). My point avoids confusion and improves clarity. I continue to strongly suggest that either the British designation be used for American rounds (APCBC), or one might state APC (armor piercing and ballistic caps). The T33 90mm APBC round is a possible point of confusion. The round is capped, but does not have an armor piercing cap, so has a different cap situation from 90mm M82 "APC". What is the U.S. designation for T33 90mm APBC? Is it AP or APC? [ 11-28-2001: Message edited by: rexford ] [ 11-28-2001: Message edited by: rexford ]</p>

Here is Kurt's response regarding the origin of U.S. 57mm HE rounds, as noted on the AFV News site: "2) If you want to know which Army Ammunition Plant made 57mm HE rounds, you'll have to ask the folks in College Park. If you are wondering whether it was British or American made, it was American. The US, as a rule, did not re-designate British equipment. For example, the 6 lb AT gun was listed as the "Mark III (British)" and the ammunition kept the same UK designators. The design of the 2-inch smoke mortar was adopted by the US, but American made mortars and projectiles used M-designations. Even into the 1990's this held true, as some 105mm rounds are listed in the tank TMs with UK L-numbers, and the M119 (or whatever) 105mm howitzer TM notes the difference in nomenclature between the US and UK markings that may be seen on caution plates and such." Good stuff, and I have thanked Kurt Laughlin many times over. One great researcher.

Kurt Laughlin, on the AFV News site, has noted that 57mm ATG fired cannister rounds, and they were more common than 37mm cannister. Another issue noted. The potential ammo types for 57mm ATG keep coming out of the walls.

Kurt Laughlin has posted information on the AFV News site giving the proper designation for 57mm ATG HE rounds: The US did have a designation for the 57mm HE round, T18E1. User instructions were issued via Technical Bulletin TB ORD 169, dated 21 August 1944, and the round was included in firing table FT 57-C-1 issued on 19 September 1944. I will ask where the 57mm HE rounds were manufactured.

The Americans may be characterize their 57mm rounds as AP and APC but it actually is an APCBC round, which fully describes the number and type of caps. To say that 57mm ATG fired AP and APC, and 6 pdr fired AP, APC and APCBC, is incorrect. I am interested in correctly describing the cap situation, so 57mm ATG fires AP and APCBC. The fact that the round has a tracer or HE filler is besides the point when one is discussing the presence of caps. So if a book says 57mm ATG fires AP and APC, 6 pdr shoots AP, APC and APCBC, they are presenting misleading information. Technically and actually, 57mm APC should be referred to as 57mm APCBC. Since the Americans did not have an APC round, they very sloppily referred to APCBC as APC (armor piercing with caps). The British practice of designating AP, APC and APCBC is what the 'Mericans should have used. 57mm ATG fires AP and APCBC interms of caps. When one is comparing American ammo to British it becomes very important to fully indicate the caps, a point some authors seem to have missed. [ 11-27-2001: Message edited by: rexford ]</p>

Advanced Squad Leader on U.S. 37mm cannister from guns: "is available in all theaters but only after 7/42." "75mm cannister .... is available in 1944-45 but not in Italy." "105mm cannister ..... is available in 1944-45 but only in the PTO". M3 light tank, M3A1 and M5A1 gets cannister. So the Americans used cannister in Europe during 1944 and 1945. As noted previously, Advanced Squad Leader did extensive research on their ammo availability rules and they were right on 57mm ATG HE and APDS 16 years ago. While a few real good calls does not mean everything is to be given the automatic okay, the references in the preceding post on cannister availability seems to support ASL on cannister for 37mm guns.

The American 57mm ATG fired AP and APCBC rounds, the Americans never used APC rounds during WW II for their tank and anti-tank guns. AP is armor piercing APC is armor piercing with an armor piercing cap APCBC is APC with a ballistic cap that decreases air resistance U.S. 57mm fires AP and APCBC. The British 6 pounder fired AP, APC and APCBC. Advanced Squad Leader noted that U.S. 57mm ATG fired APDS and HE during 1985, 16 years ago. Took the rest of the world quite a while to catch up, I'd say.

The data quoted by the U.S. military for 6 pdr APDS in Jeff's post is a little off the mark, which could be due to "hearsay" info handed down from one person to another. 6 pdr APDS has a 28.5mm tungsten core diameter and was fired at 4000 fps, somewhat difference from 2 pounder round (40mm) fired at 4200 fps. These things happen.

Robert McNamara went through U.S. Army ammunition use tables, which were made out on a monthly basis by U.S. units during WW II. He found evidence of 57mm anti-tank gun use of APDS and HE. Together with Jeff's find, it is apparent from Mr. McNamara's work that 57mm ATG did use APDS and HE regardless of what can be found in British sources about ammunition given to U.S. troops. It would, however, be good to find something in British sources about the total number of rounds (HE and APDS) shared, but it appears a "done deal" that some sharing was accomplished. It is also obvious that previously published descriptions of ammunition available to 57mm ATG may now be somewhat outdated, due to unfamiliarity with newly found sources since the "limited to AP/APCBC" ammunition reference for 57mm ATG was made.

The range at which a target is hulldown makes a world of difference. If a Tiger is hulldown at 5 yards you hit it every time which is the same percentage against the full tank target, if a Tiger is hulldown at 2000m you hit it alot less on a percentage basis than the entire tank target. The vertical and lateral spread of shot attempts widens at an exponential rate as the range increases. But the rounds are spread around the aim point with a bell-shaped distribution curve. Say the target is a 9' high target and the turret is 4' high. Assume the shot probability puts 85% of the attempts within 1m of the target center of mass at 500m, and 15% at 1200m (assume all shots are within the width dimension of hull and turret for ease of calculation). At 500m, the hit probability against hulldown turret alone is 61%, hit probability against entire tank is 96%. At 1200m, hulldown turret hit percentage is 9%, entire tank target is 21%. At 500m, hit chance against hulldown turret is 64% of entire tank, at 1200m the ratio drops to 43%. If a gun puts 50% of shots within 1m of aim point at 500m, which is about what CMBO assumes for many weapons and ammo, chance of hitting 4' high turret is 31%, probability of hitting entire 9' high target is 66%. As the hit percentage drops, the chance of hitting the hulldown turret compared to the entire target reduces to the ratio of the areas. As the hit percentage climbs, the two percentages close in on one another. Now, if CMBO assumes that a high percentage of the misses occur because rounds fly wide of the target, which is reasonable, then the 500m hit percentage of vertical errors would be around 85% or so. Based on our calculations, at 500m the difference between hulldown and fully exposed should be fairly large. At 100m there should be almost no difference cause the trajectory spread of shots just don't vary much from gun to target.

The range at which a target is hulldown makes a world of difference. If a Tiger is hulldown at 5 yards you hit it every time which is the same percentage against the full tank target, if a Tiger is hulldown at 2000m you hit it alot less on a percentage basis than the entire tank target. The vertical and lateral spread of shot attempts widens at an exponential rate as the range increases. But the rounds are spread around the aim point with a bell-shaped distribution curve. Say the target is a 9' high target and the turret is 4' high. Assume the shot probability puts 85% of the attempts within 1m of the target center of mass at 500m, and 15% at 1200m (assume all shots are within the width dimension of hull and turret for ease of calculation). At 500m, the hit probability against hulldown turret alone is 61%, hit probability against entire tank is 96%. At 1200m, hulldown turret hit percentage is 9%, entire tank target is 21%. At 500m, hit chance against hulldown turret is 64% of entire tank, at 1200m the ratio drops to 43%. If a gun puts 50% of shots within 1m of aim point at 500m, which is about what CMBO assumes for many weapons and ammo, chance of hitting 4' high turret is 31%, probability of hitting entire 9' high target is 66%. As the hit percentage drops, the chance of hitting the hulldown turret compared to the entire target reduces to the ratio of the areas. As the hit percentage climbs, the two percentages close in on one another. Now, if CMBO assumes that a high percentage of the misses occur because rounds fly wide of the target, which is reasonable, then the 500m hit percentage of vertical errors would be around 85% or so. Based on our calculations, at 500m the difference between hulldown and fully exposed should be fairly large. At 100m there should be almost no difference cause the trajectory spread of shots just don't vary much from gun to target.

Not implying, stating that evidence exists that U.S. 57mm ATG were getting and using APDS. U.S. tests disclosed that 57mm and 17 pounder APDS was extremely inaccurate and wild, so I doubt that ATG crews would view the round as anything but a last ditch survival attempt. Advanced Squad Leader rulebook is not perfect, and has some things that appear far-out (like 57mm ATG APDS). But I have communicated with Robert McNamara alot on a variety of ASL rulebook items and he has the references for where many of his findings came from. Plus there is a U.S. firing test against Panther in Europe (summer, 1944) where 57mm ATG fired APDS and the round was listed on the firing test inventory as "normally available", whereas 75mm HEAT was listed as "special". Limited availability for ASL means only a few rounds per gun, on average. Sorry, no specifics on total number of 57mm HE rounds in inventory. The problem with HE is that is normally does not have a ballistic cap, so drops velocity faster than APCBC. (aside: Smoke has a flat nose, and a really low velocity, so smoke shots would be on another planet altogether). AP sight markings would probably be closer to HE than APCBC. Finding velocity for HE rounds will take me some time.

Robert McNamara, who did the armor system development and research for Advanced Squad Leader, noted the following ammunition for WW II 57mm ATG: Limited availability HE starting June 1944 Limited availability APDS starting June 1944 AP and APCBC types Robert went through WW II official ammo use tables which were made out each month, and he found these tables at Aberdeen Proving Grounds. 6 pdr ATG HE was available during February 1943, based on Advanced Squad Leader, in limited quantities. APDS and HE would be fired even though they were not on the gun sight range markings using any one of a number of systems. The British fired APDS from 6 and 17 pounder guns without APDS range markings by setting a ratio of the estimated range to the range setting to use with APDS. Last winter something found a post-WW II manual for the Achilles where they indicated that APDS was not on the gun sight but firers were to use 60% or so of the gun elevation for APCBC. Something similar could be used with HE and APDS for 57mm ATG. U.S. 76mm and 90mm gunsights did not have HVAP but they still fired the rounds accurately, by using a conversion system.

The finding derived from the U.S. firing tests against three Tigers, and British tests that result in the same conclusion, indicate that the armor equalled U.S. penetration test plate, which allows direct comparison between TM9-1907 data and Tiger armor.