Paul Lakowski

<BLOCKQUOTE>quote:</font><HR>Originally posted by Kurtz: Could you please explain this, I don´t understand what you mean by depth in this context. Do you by any chance mean diameter? I that case it makes sense to me. <HR></BLOCKQUOTE> Yes the depth is meant to be diameter.

I'm going to have to get a website to start explaining some of this stuff with graphics like Markus [ COOOOOOL].Yes the 105mm was a modern HEAT round for the M-68 /L-7 gun with a standoff probe.This may be part of the problem , since in a WW-II shell / sloped plate interaction the warhead may have an increased standoff 'built in' by the increasing slope of the plate.This in turn may increase or reduce the penetration depending on the original warhead standoff compared to the optimum standoff for that warhead design & liner material . Johns right that Jet penetration works in a hydro dynamic manner but while the initial jet tip velocity is 7-8km /s the tail is as slow as 2-3 km/s. In addition the above figures are idealized velocities through air. While penetrating a armored target the penetrating velocities are slowed down by about 2/3. A ultra long rod model [ konrad Frank recons 100:1 L/d -rod lenght to diameter] can be used for simulating jetting but must include the jets compressiblity . In any rod impact the tip is going to be damaged by initial contact with the armor but studies confirm that any nose plate interaction problems should disappear after 2 projectile diameters of penetration. When the jet impacts, the material of both the jet and the plate flow together radially outwards in all directions creating a debre field through which the jet must continue to penetrate until cleared.This process can take upto 50 micro seconds or 1/8th of the penetration time. When this is a spaced plate @ 45° ,the effect can be considerable making the spaced plate effectiveness about 3 times the plate thickness independant of standoff. Now since the efficency per unit lenght of a HEAT jet is around 0.5-0.7 [copper] that means the first 3-4 rod [jet] diameters or about 1/25th of the jet lenght or penetration is effected .If you average this out thats 1 x 0.33 + 24 x 1.0 ÷25= 97% @ 45° . Compared to the tests I quoted above that sounds about right. Now these test are for 60s/70s technology 'Precision charges', so we need to know more about WW-II SC before anything definate can be stated.For one thing its clear that WW-II jets were about 1/3 as efficent as 'precision jets' mainly due to stetching. This would suggest that the 'rod/jet is 1/3 as long and the 'damage from sloped impact'would propotionally be more say 0.33 + 8 ÷ 9= 93% & 45°. Jentz figures for German HL HEAT at angle are [ normalized to 0°] <PRE> 0° 105 1.0 = 1.0 30°100 0.95 ÷ 0.866 = 1.1 45° 80 0.76 ÷ 0.707 = 1.08 60° 50 0.48 ÷ 0.5 = 0.95 </PRE> For every paper on shaped charge we have 10 on KE , so we know alot less about HEAT than KE.

<BLOCKQUOTE>quote:</font><HR>Originally posted by CommanderC: 19 Echo: I don't think any modern Soviet tank round is superiour to our 120 mm DU sabot rounds. Hence my frustration with the eagerness of the NTC and modern tank sim designers to give T80s and T90s souped up power in regards to M1A1 armor penetration. <HR></BLOCKQUOTE> The BM32 performance equals that of the M-829 round.

Wow Markus is here thats an improvement! A couple of points All; projectiles will ricochet even HEAT the question is at what angle and what velocity and - in the case of HEAT - if this is before or after HEAT JET detonation and stretching[ ~1/3 millisecond]. HEAT is effected by slope but its not completly clear how. Robert Livingston told me that 105mm HEAT was tested on Panthers Glacis and achieved penetration when the warheads supposed to do only 4.5 inches[?]. Int.J.Impact Engng,Vol22-pp328 Shaped Charge Jet studies <PRE> 0° 100% 45° 97% 60° 94% </PRE> Rheinmetall Hand book on Weaponary ....[figure 1128]relative penetration of 105mm projectiles...... <PRE> 10° 30° 45° 60° AP 1.05 1.3 1.77 2.5 HVAP 1.03 1.25 1.84 2.68 APDS 1.02 1.24 1.63 2.11 HEAT 1.02 1.14 1.37 1.96 LOS 1.02 1.15 1.41 2.0 </PRE> None of the warheads has the same penetration as the LOS suggest,most are more but HEAT is less-except for 10°. ARMY & WEAPONS #50 pp33.... Chinese and Czech 100mm gun warheads... <PRE> 1000m 2000m 0° 60° 0° 60° BK-354M 280mm 110mm 280mm 110mm ZBK 5M 390mm 150mm 390mm 150mm BR-412B 152mm 64mm 134mm 54mm PSv 171mm 65mm 146mm 55mm PrSv 335mm 168mm 335mm 168mm BR-412D 175mm 71mm 156mm 63mm BK-354M 264mm 100mm 237mm 90mm </PRE> Chinese PrSv is the only one with 60° penetration the same as the LOS suggests. The difference in the HEAT performance could be due to the standoff effect. [This message has been edited by Paul Lakowski (edited 09-02-2000).]

None of the M-1 hulls are as heavly armored as the front turrets are. This is a growing trend in modern tank design and as a rule all M-1 s can be penetrated by BM-32/42 at short range through the front hull.As to HEAT some are warheads capable of penetrating the hull , it all depends on how much fuel is in the front tanks as these contributes almost half the HEAT protection.

The effect the angle has to do on the projectile has to do with several factors . The CRH[shape of nose IE long and pointy or blunt] value is important. In addtion the lenght to depth ratio[L/d] of the projectile is important as the effect on slope is in the nose, the longer the projectile the less this effects sloped armor. As a rule long pointy projectiles take a longer route through the armor compared to blunt ones, but the higher the L/d the lower the effect.

<BLOCKQUOTE>quote:</font><HR>Originally posted by Rattus: Thanks Paul, can you clarify your post a little for me please, you are referring to the striking velocity against the first plate(?) and saying that at the mv of 800+ m/s with the plates space 20+ calibres apart the resistance of the second plate iceases with initial striking velocity until at c1000/ms the resistance is effectively 10(100?)%?<HR></BLOCKQUOTE> No thats the target as a whole, buy 1100 m/s its 20% for AP type warheads , while APFSDS is ~ 10% loss over 1.2 to > 2.0 KM/s. It makes a big difference , Ogorkeiwcz reports that spaced plates reach about 1.2 Em compared to solid RHA of the same mass. <BLOCKQUOTE>quote:</font><HR> Just to expand here it should look roughly like this . <PRE> standoff 1-3 4-5 6-7 8-10 15-20 [in projectile diameters] Relative change -10% -20% -10% 0% + 10% </PRE> Its been noted that slanted spaced impact is more severe than normal impact as YAW plays a role.In the case of Ogorkiewcz's 1.2 , he's probably refering to LEO-1A3 which features about 20-30cm air gap beteen the first and second plates. This amount of space Vs APFSDS is only going to offer 8-10:1 projectile diameters, which should offer no change in resistance. So clearly the rate of 'tumble' in the rod is significant. <HR></BLOCKQUOTE> John got RIcks Email , not sure about 241mm @ 30o must have been against substandard American 240 BHN target plate. If we can get Jim & Rick [ & Steve Zaloga]here, maybe we can re invent the 'Tankers Net' He He He [This message has been edited by Paul Lakowski (edited 08-28-2000).] Second edit at coffee time ] [This message has been edited by Paul Lakowski (edited 08-28-2000).]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Rattus: "you find the test of the KWK43 against the Tiger II frontal turret armour which it perforated completely (185mm). It exited the tank through the rear turret armour (80mm IIRC = > 265mm at nearly the vertical) (8^). Now this could be within 20% of 230mm vertical penetration value @ 100m but how would you stretch this to 170mm?" The thickness of multiple armour plates are not straightforwardly additive. I think a good rule of thumb works out to be 1/2 the thickness of additional plates - so in this example it would only be effectively 225mm - which is very close to 20% of 170mm. Furthermore, the inside of the rear armour plate wuld not be face hardened. Note the above rule of thumb dooes not work for laminated plates. <HR></BLOCKQUOTE> This is true when the airgap between the plates is quite small say 1-8 projectile diameters , but when this distance reaches 20:1 or more and the striking velocity exceeds 800m/s the overall resistance goes up so by 900-1000m/s its 10 % , thats from actual test.

<BLOCKQUOTE>quote:</font><HR>Originally posted by :USERNAME:: At 2000 meters the panther HE is traveling at 650 meters a second? It had to be deadly accurate. I bet you could walk some into a window of a building at that range. Very scary. If I wasnt so tired I would use this data to find time of flights. A 75mmL48 AP takes 1.44 seconds to go 1000 meters and reaches a height about 2.5 meters max. Its INITIAL velocity is 750 meters a second. So a panther 75mm HE would take less yet its the same shell really. I find this crap too fascinating. I should have my head examined. Lewis<HR></BLOCKQUOTE> No Lewis, when you start dreaming up formulas to solve the intractable problems of terminal ballistics [ like I did last nite] then you need your head examined

<BLOCKQUOTE>quote:</font><HR>Originally posted by cbo: You must have blinked, John - it is even worse : 500yds - 208mm 1000yds - 192mm 1500yds - 176mm Hunnicutt p. 565. <HR></BLOCKQUOTE> In the Ordnance board report the values for 17Lb APDS into 'homo plate' are reported to be <PRE> 0° 30° 500 yrds 250mm 208mm 1000 yrds 232mm 191mm 2000 yrds 192mm 161mm </PRE> I was looking at Hunnicutts Pershing book and the 90mm ammo diagrams that Claus posted to the TANK NET. Claus could you post the link here? The US projectile tips look different than the German, the 90mm APCBC has a tip to rod diameter ratio of 9:1 compared to ~ 4:1 for german APCBC rounds while the HVAP shot is 14:1 like the british APDS and different from the german AP 40 type shots which are ~ 9:1 for the 75 and 88mm guns. May be this has an impact in sloped penetration , in the diagrams the difference between 30° and 0°at 1000 yards seems like 1.25 for this APCBC round. We know from APFSDS work that theres a hugh difference in penetration route of a pointed rod compared to a flat tipped rod - flat tipped rods take a shorter route through the armor while sharp tipped rods take a longer [ Vs thin plates at sharp angle IE 70°]. This is similar to what happens with ricochet- sharp tipped rods ricochet at lower velocities than flat tip rods. So in short the sharper tipped projectiles get better penetration Vs vertical plate but suffer more Vs slanted armor. [This message has been edited by Paul Lakowski (edited 08-26-2000).]

Yes its good to see Andrew and Claus . John theres no conspirecy only discussion.What I object to is 'selective use of data' from various sources and dismissing the rest as false or faked, from source that most of us respect. If CM data from Sopwiths formula is the same as the data Claus reports for normal impact this suggest there using the same penetration criteria which looks alot like the 50% ballistic limit value. It seems the problem here is the angle , this is exactly what Robert warned me about. In the Ordnance board report they suggest the only way to do a real estimate is on a shot by shot basis, so that part of their approach is sound.The problem here ofcource is that normal impact is rare and angled [ or compounded angled] hits are the norm. Karl reports the 88 Vs Tiger -II test was at 400m range and examination of the impact shows the front hit about 4 projectile diameters from the gun embrassure which should reduce the front plate armor efficiency to 0.75.The plate hardness is 220 front and 290 BHN rear plate [from Claus website].Going on the previous data on hardness, thats ~2% loss per 10 BHN @ 1000m /s range or 11% loss [275 BHN=> 220BHN] on the front plate leading to 19cm [LOS]x 0.75 x 0.89 = ~12-13cm The rear plate is 8cm @ 20° [x1.2] or ~9-10cm rear plate.Thats 21-23cm total penetration to say nothing of the fact that the penetration of multiple plates has been shown to reduce total penetration by about 10% @ 800-1000m/s if the gap is 20 times the projectile diameter at normal impact angle.As I see it the gap between front and rear plate is around 35 times the 88 diameter.Thus the penetration needed to achieve this event is on the order of 22cm x 1.1 or ~23-25cm . Now if we look Claus’s data @ 500m 0° both figures are 205mm average penetration or ~ 209mm @ 0° @ 400m range . 2/3 of hits should then result in ± 8% ballistic limit range. This~ 70m/s difference is like a 500m range change, which on the 88L71 is about 20mm difference or 189-239mm . In 80-90 % cases the value is ± 100m/s change in the ballistic limit , thats ± 900m range or 37mm penetration =172-246mm.range . The extreme 10 % of cases should result of ± 200m/s , which is the same as a <1500m range change or 54mm penetration = 263-155mm range.

Sure is good to see Andrew . Looking at the primitive photos and diagrams of the 88mm rounds I get.[Jentz 'Germanys Tiger tanks'].The 88 Pzgr 39/KwK 36 [Tiger 1] has what appears to be 396mm long ogive 4.5:1 L/d projectile with a 0.25-0.26 tip to body diameter or about 4:1. Looking at other German warheads this is similar to the all the German 75mm Pzgr rounds.For the 88 pzgr 39/KwK 43 [Tiger 2 ]I get 0.19-0.21 or about 5:1 tip to body radius. Rereading Brooks work and examining the accompaigning pics its evident that at the transition velocity where the penetration curve 'rebounds' seems to conform with the projectile penetrating in a 'Yawed' fashtion. Looking at the Int.J.Impact Engng Vol-23 pp 723 -734. Piekutowski et al. They seem to be showing the same event with ogive Steel 10:1 rods impacting aluminum targets. This is ridgid penetrator vs ductile target models. In addition in both Brooks and Piekutowskis work ,the penetrator with the harder metal delayed the onset of this transition velocity and achieved higher penetration overall and a sharper penetration - velocity curve. So even a small change in the ballistic cap of the 88L71 combined with higher velocity could have resulted in a much higher penetration, compared to 88L36 round. What I suspect is going on is that the exact deformation of the ogive is creating an imbalance in the penetration leading to this 'Yawed' type penetration. In all cases [ so far checked]with flat tip rods or ogive penetrators with completly deformable tips , there is no noticable transition zone.

<BLOCKQUOTE>quote:</font><HR>Originally posted by Juardis: That's why I said in an earlier post to this thread that ideally, you'd want all the data from a single source. However, you guys have seemingly given a plausible explanation for why the 88L71 penetration data is greater than other data. If true (that there is a physical reason the test data is an outlier), then this suggests the equation is good for everything BUT the 88L71. Even so, and I think this has been mentioned already, it doesn't mean diddly in CM1. Depending on the ranges in CM2 though, it could mean diddly . I love this thread. What I'd like to know though is does the Covington and Aberdeen data show a similar "bump" in the curve? (Remember, ideally you want to use ALL the data from ONE institution, not all data lumped together). <HR></BLOCKQUOTE> Jeff in theory if you know the testing criteria you can 'normalise' all the data from different sources ....the engineers do it all the time. To that end, here's some data on projectile vs common targets of varing hardness at increasing velocity. The results are all referenced to RHA being a value of 1.0 and are from the "Journal of Materials Processing Technology"- Vol96 , pp 81-91. <PRE> Steel 400m/s 800m/s 1200m/s 1600m/s [110 BHN] 0.5 0.67 0.77 0.8 [280 BHN] 1.0 1.0 1.0 1.0 [ 430BHN] 1.8 1.57 1.38 1.25 </PRE> This suggest the change in BHN at each striking velocity should be [ over 110-430 BHN ]. <PRE> 320/130 = ~4 % every 10 BHN change @ 400 m/s [1320 ft/s]. 320/90 =~3% every 10 BHN change @ 800 m/s [2640 ft/s]. 320/61 = ~2% every 10 BHN change @ 1200 m/s [3960 ft/s]. 320/45 = ~1% every 7 BHN change @ 1600m/s [5280 ft/s]. [This message has been edited by Paul Lakowski (edited 08-25-2000).]

This is from Karl Brandel. "you find the test of the KWK43 against the Tiger II frontal turret armour which it perforated completely (185mm). It exited the tank through the rear turret armour (80mm IIRC = > 265mm at nearly the vertical) (8^)." Now this could be within 20% of 230mm vertical penetration value @ 100m but how would you stretch this to 170mm?

Finally some one is beginnig to see the nature of just who hard the problem is, Thanks Rattus <BLOCKQUOTE>quote:</font><HR>Originally posted by Rattus: I understood the US Army usd the "through crack" ballistic limit until the end of WWII and thereafter introduced the "specified damage to thin reference plate..." limit. It did not use the US Navy's ballistic limit of "complete penetration". <HR></BLOCKQUOTE> Yes you might be right, but Claus Bonnesen posted a set of 90mm ammo charts , that clearly state 'NAVY criteria' on the top right had corner....so if anything this complicates matters further.I'll have to dig further cause I remember reading that this was changed in 1955. Can any one tell what criteria Sopwiths formula is based on? <BLOCKQUOTE>quote:</font><HR> This means that penetration figures even for US Army equipments tested before/during and after the war are not directly comparable. I assume(!) the British tests used the "complete penetration" limit - their naval testing was obsessed with penetration with shell remaining in a condition fit to burst. <HR></BLOCKQUOTE> So that suggests that 80% success like the Russian tests. I remember the Charm 3 round for the Challenger -2 was listed as 700mm @ V50 ballistic limit @ 2km range...I guess they changed some where along the road. <BLOCKQUOTE>quote:</font><HR> Unless the Germans also used comparable ballistic limits the German proof figures are not comparable to those conducted by the US and UK. Different German proof test may also have had different ballistic limits. Even if they all used (for example) the "specified damage to thin reference plate..." ballisitc limt, there is enormous scope for difference in the required amount of damage to the reference plate and the distance the reference plate was positioned behind the armour plate. The fact that target plates have different brinnel hardnesses is another problem (I assume the plates were face hardened). If the plates were not of the same quality (metallurgical flaws, rather more important for face hardened armour than homogenous armour), if the plates were not of constant hardness, to what depth did the hardening extend - how deep was the transitional layer...Again unless these are constant between the different testers the comparisons are very difficult. Finally, whilst the ogive, hardness and nose height (as Paul noted) are important and will effect penetration of otherwise identical shells, the same is also true of the shape and hardness of the armour piercing cap against face hardened armour. This is complicated by the fact that the shape/hardness of both cap and shell will be more or less optimised (effective)for a particular range of impact angles. A design which works well over (say) 0-30 degrees will not be as effective over 30-60 degrees, so whether you perform the test at 30 degrees or 0 degrees is important. The shape, particularly of the cap, is also important in detemining if the shell richochets or not - especially when considering impacts at higher angles of impact. Simple scaling of results to compensate for differing slopes will not suffice even for the same projectile, let alone ones with different ogive/caps/hardness... My point is that proof tests such as quoted earlier by different testing bodies are extremely difficult to compare without prodigious ammounts of imformation, probably no longer available. The values given for the penetration of the 88/71 therfore do not seem to be inconsistent given the variables discussed above (and I did not mention shell quality, barrel wear..). The Jentz figures do not have to be "wrong" (or anyone else's), they may accurately represent a particular behaviour under what are unique circumstances (that series of tests). This might mean that CM is lousy at modelling that situation but great for the other 95% of the time. Since the aliies do not seem to have produced a gun/shell with sufficiently similar shape/hardness/calibre/velocity to that of the 88/L71 at the same velocity an easy test comparison is impossible. Michael<HR></BLOCKQUOTE> I couldn't have reported it better I would only add that Jentz touches on German test methods, and the implication [ that I read] is that they take a average of a number of shots to determine a value , which sounds exactly like the methods reported in the Impact Engineering Journals. In the journals a simple test involves 3-6 shots with the data point being the average, but I understand this small number is only possible with aid of computer sims. If you read the material on 's curve' distributions I mentioned before they use some thing like 70-150 test shots all on the same target obliquity and range etc.

Heres a link to the Tank NEt where I posted some Jpegs of the 'S curve' used to determine 'ballistic limit' values and a basic idea of 'some of the penetrating critera'[Zukas , Impact Dynamics]. Robert wrote more extensively 'bout this I'll see if I can find it. And I recall Jentz has a paragraph 'bout some of the german techniques in his latest works ,which I don't have in front of me.If anyone else has it handy maybe they could post it. Included is a similar Jpeg for APFSDS[int. J.Impact Engng] [url="http://www.tanknet.org/ubb/Forum3/HTML/000033.html"]http://www.tanknet.org/ubb/Forum3/HTML/000033.html[/url] [/html] Heres the link to the Int.J.Impact Engng, if you guys are serious about ballistics you need to subscribe to this. [HTML] [url="http://www.elsevier.nl/inca/publications/store/7/0/0/700.bio1.shtml"]http://www.elsevier.nl/inca/publications/store/7/0/0/700.bio1.shtml[/url] [This message has been edited by Paul Lakowski (edited 08-25-2000).] [This message has been edited by Paul Lakowski (edited 08-25-2000).]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Simon Fox: Will someone please answer Lewis's question as it seems pretty pertinent.<HR></BLOCKQUOTE> WHos Lewis , I looked back through two pages and didn't see his question?

<BLOCKQUOTE>quote:</font><HR>Originally posted by Big Time Software: 1. Do agree that several different, and independently credible, sources have produced different results for the same weapon? <HR></BLOCKQUOTE> YES <BLOCKQUOTE>quote:</font><HR> 2. Do you agree that it is impossible for different sources to come up with different results if all are based on the same testing standards? <HR></BLOCKQUOTE> Yes and No , Cause there not baced on the same penetratio criteria and the ones that are close are well within one standard deviation of expected results. <BLOCKQUOTE>quote:</font><HR> 3. Do you agree that it is inherently flawed to pick one set of the credible numbers over another set without any other reason than blind faith that the one you are picking is correct? <HR></BLOCKQUOTE> It doesn't matter what data points you choose as long as the modle includes a normal distibution and the test data is adjusted for test conditions.And adjusting for differences in each sides testing criteria . <BLOCKQUOTE>quote:</font><HR> 4. Do you agree that our physics model is only in dispute in relation to the 88L/71 data that you support. Not to any other data from any other weapon from any other nation? <HR></BLOCKQUOTE> Not nessesarily I haven't yet look at the others, yet. <BLOCKQUOTE>quote:</font><HR> 5. Do you agree that if our equations are incorrect that means that all other data it produces is also incorrect? <HR></BLOCKQUOTE> Quite possibly, but again if the normal distribution of expected results is there it might be adjustable, and fit. <BLOCKQUOTE>quote:</font><HR> 6. Do you agree that there is a credible set of test data, for many guns from many nations, that agrees with our mathematical equations' output? <HR></BLOCKQUOTE> No unless you use the 'modern research method 'as thats the only one that is . <BLOCKQUOTE>quote:</font><HR> 7. Do you agree with the scientific approach that when you have differing data, from credible sources, that you must look to another scientific (or primary source) to explain which of the conflicting data sets is correct? <HR></BLOCKQUOTE> They are all correct if taken from the right point of view accounting fo test conditions. <BLOCKQUOTE>quote:</font><HR> 8. Do you think it is more probably that there is one set of questionable data for the 88L/71 or that all the other test results, for all weapons from all countries, is in error? <HR></BLOCKQUOTE> Not likely see above. <BLOCKQUOTE>quote:</font><HR> 9. If our equations are outdated and inaccurate, can you please explain how it is that our results match those of test data from three different nations for dozens of guns? Put another way, how can a flawed set of equations come up with the correct results and still be flawed? <HR></BLOCKQUOTE> In sufficent data to answer that question at this time. <BLOCKQUOTE>quote:</font><HR> 10. Which is more credible; blind faith that can not account for differing data or mathematical results, or a reasoned scientific approach that can account for everything using primary materials AND mathematical computations? Steve<HR></BLOCKQUOTE> Math approach is best if its done right and accounts for the test results. [This message has been edited by Paul Lakowski (edited 08-26-2000).]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Big Time Software: Helge, Jentz and Hogg are the closest ones to one another. They are similar at 500m and 1000m, but start to differ significantly at 2000m (by 5.3%). WO185 differs even more from Jentz beyond 500m. At 1000m the difference is 2.4%, and at 2000m it's 9.1%! Oh boy now we get to WO219 which is different from everybody. Comparing to Jentz, we get a 3.8% difference at 500m and a whopping 17.9% difference at 1000m. This is HUGE! And I haven't even mentioned the Bovington numbers yet. So stop acting as if the Bovington numbers are a single outlier. Clearly - and we're using the data that you provided, Helge - none of these data sets agree. The other four are not close to one another. Some of the differences (up to 17.9%!!!) are major. Is 17.9% enough variance for you to consider it significant, Helge? How can you overlook a difference that large? In fact, WO219 gives a penetration value at 1000m for the 88 L/71 that is less than the value given in Combat Mission! If I am to take you at face value and "just use the published figures" then perhaps I should choose WO219 and lower the capability of the 88 L/71 in CM even further? By your reasoning, this is what I should do. To sum up, the published figures - not even considering the Bovington data - are NOT close to one another. They do NOT agree. Even your own figures clearly indicate that you are wrong. <HR></BLOCKQUOTE> There is no wrong data just wrong interpretations of the data. Armor penetration follows a normal distribution so that the ballistic limit value is actually a average of a whole number of results from any given test firing at a given range and angle of attack. The variation on this is up to ± 40% for AP type shots at ordnance and sub ordnance velocity.If you truncate the results to the most likely 80-90% , the values is ± 20°. With about 2/3 of results being ~ ± 5%. However to compound things each country uses its own defination of what is a 'complete penetration' and 'partial penetration'. The USARMY used the US NAVY standard untill 1955[ I think?] . This standard classifies penetration as when the projectile completely clears the plate and penetrates a 'witness plate' behind the armor. This roughly corresponds to 75-80% of hits successfully penetrate, which is similar to the Soviet standard which is ~ 75%.... In other wards penetration is not reported to occur until that many complete penetrations occur. Afterwards they changed to the 'inital breaking point' which corresponds to ~ 20% of hits penetrating. The Germans and most modern armies and researchers use the 50% ballistic limit value cause its the easiest to determine accurately. I'm not sure about the brits as theres was ~ 80% for the 2Lb, but I was always told it was 50% like the Germans. So what does all this mean ... If your data is American or Soviet from the 50s it may be under rating penetration by ~ upto 20%, when compared to German or research data.

WHY WAS MY LAST POST DELETED??????:/

The reason the 88L71 could have different results from the test is because the ratio of the tip to the ratio of the body of the round is about 6-7:1 while the ratio of the Tip to body of most other german APCBC rounds is 4:1 In the test that Brooks did this difference could be signififcant . In addition the tests with various materials showed no correlation between increasing density or hardness and increasing penetration infact in some cases the opposite occured. In addition Brooks work showed that the hardness of the cap had as big an impact on the penetration results as did varing the tip radius....in the transitional zone. This ratio may well explain the superior performance of WC penetrators as they reach tip to body diameters of 14:1 or more. Sources: "Ballistic Impact - The dependence of the hydridynamic transition velocity on the projectile tip geometry" PN Brooks Def,Research Est, Valcartier Quebec. Oct 1974. "Ballistic Evaluation of Materials for Armor Penetrators" PN Brooks & WH Erickson ef,Research Est, Valcartier Quebec. Oct 1971. At this point these are the most important as they deal with 'ogive penetrators 4.5:1 L/d striking at 1400-4500 ft/s'. But theres also evidence of something funny going on with steel 3:1 cylinders penetrators at around 1000m/s impactimng IT 80E plates in A Tate's 'Long Rod Penetration models - Part II extensions to the Hydrodynamic theory of penetraion RARDE 1986 , Int.J.Mech Sci Vol 20, pp 599-612. I'll start searching the jounals for more AP data as normally I'm just interested in long rod penetrators and shaped charges. Since half the papers in these journals are about AP projectiles @ sub ordnance and ordnance velocities it shouldn't be too hard.

People stop using the Ordnance board report as good science and physics...NO ONE USES THIS FORUMLA ANY MORE. Ive never seen any reference to it in the 'abstacts' of the papers that I look at. This is a 50 year old formula , which already makes it suspect, cause no formula survives more than 5 -10 years in the engineering journals before its ripped to pieces and rebuilt to better explain the events. The inconsistancies we've stated above would be more than enough to send the researchers back to the drawing board. None of us are ballistic researchers , so we have to go to the sources. I'll start digging throught the mountains of journal to see what I can find , I suggest you all go do the same and then may be we'll all get some rest and somewhere. I'sorry but the burden of proof has always remianed with BTS.If I go to some interested third party and say that Jentz , Hogg and others consistantly report the same data for a round of ammo , while this CM game claims -to the death I might add- another completely different value .... who do you think there going to believe?

I think you all need desperatly to get a hold of some modern engineering journals like the 'Int. J.Impact Engng ' or the 'Int. Symposium on Ball'. Charles Anderson Jr has lead over a decade of research perfecting a simple penetration formula that currently covers penetrators with L/d of 5:1 upto 40:1 ranging from striking velocities of 800-1000m/s right up to 1800 m/s. Its prediction ability is baced on lenght and is uncannly accurate and is universally accepted as the method to anaylse all penetration.Its only a matter of time before the research is expanded to include shaped charge and AP type penetration . For my part I'm going to see if it can be adapted to include APDS and then APC . I will ask about falsified 88 data ,but in the end I'm sure I'll find that all the data points can be put on a regression line just by finding out things like plate dimentions in relation to projectile dimentions or adjusting for projectile shape. I did some preliminary measurements and the 88 seems to have tip to rod diameter of ~ 6-7 :1 which is markedly different than other APCBC[ ~4:1]. It also may be that the penetration abilities of HVAP and APDS may be more tied to this factor as there ratios are in the 14:1 range. I wish you luck with your game as it seems to be reviving the wargaming industry along with our game 'Steel Beast'.

<BLOCKQUOTE>quote:</font><HR>Originally posted by Big Time Software: Incorrect. Penetration is proportional to mass, which correlates with projectile length. And I didn't say anything about diameter, so I don't know who you're responding to about that. Penetration is inversely proportional to diameter, all else being equal. Charles<HR></BLOCKQUOTE> Penetration is proportional to mass , is it ? Thats why in Brooks tests three projectiles of the same dimentions [ 4.5 :1 L/d ogive penetrator with 0.35 “ x 1.71” dimentions ] made of Tungsten carbide [ 14.7 g/cm³] , Tungsten Alloy [ 17.3 g/cm³] and Uranium alloy[18.5 g/cm³]. All the projectiles where fired from the same gun at the same target [ Type 4340 - Rc 30-32] over striking velocity of 2000 f/s upto 4500 ft/s. If penetration was propotional to mass the heaviest should have penetrated the most,heres the results... <PRE> Tungsten carbide[Rc 74] 1840 ft/s = 0.8” 2264 ft/s = 1.73 “ 2639 ft/s = 2.05” 3017 ft/s = 2.52” 3367 ft/s = 2.97” 3721 ft/s = 3.42” 4405 ft/s = 4.41” Tungsten Alloy[Rc 31] 1862 ft/s = 1.34 “ 2600 ft/s = 1.4“ 3322 ft/s = 2.07” 4024 ft/s = 2.28” 4301 ft/s = 1.67” 4619 ft/s = 1.93” Uranium alloy[Rc 50] 2125 ft/s = 0.47” 2503 ft/s = 0.94” 2903 ft/s = 1.91” 3236 ft/s = 1.85” 3584 ft/s = 1.83” 3914 ft/s = 1.81” 4484 ft/s = 1.93” Steel [ Rc 60] 1940 ft/s = 0.89” 2717 ft/s = 1.46” 3053 ft/s = 1.63” </PRE> In all velocities the lighter WC projectile out penetrates the heavier WHA and U²Mo projectiles , while the ultra light steel projectile matches the penetration of both the heavier WHA and U²Mo alloys at ~ 2700 ft/s . Note how increasing velocities doesn’t always generate increasing penetration. From Brooks other work at 2700 ft/s that vary the projectile tip diameter the WHA penetration changes as follows.....[ test conditions exactly as above]. <PRE> 0.0001 = 1.5 “ 0.002 = 1.8” 0.1 = 1.78” 0.2 = 1.6” 0.35 = 1.1” 0.5 = 0.9” 0.35 with WC tip = 1.7” </PRE> Reality is never as simple as a formula, and the 'balls in your court' to prove that the 88L71 penetration data is wrong ,cause its been doctored. [This message has been edited by Paul Lakowski (edited 08-23-2000).]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Big Time Software: Paul, And because I don't have fully credible and complete sources for this information for all (or even most) guns in the game, the test data simply cannot be fully trusted. <HR></BLOCKQUOTE> Why? Since when was formula data more reliable than test data? <BLOCKQUOTE>quote:</font><HR> I'm not saying that a high-speed effect doesn't exist, but simply that there are other German rounds (e.g. 75 L/70) that are very nearly as fast as the 88 L/71, and yet they fit in almost perfectly with the equations that CM uses. The 88 L/71 is only about 10% faster than the 75 L/70, and yet you guys are suggesting that this mere 10% suddenly transforms the whole penetration process dramatically. I'm sorry but I just don't buy it. I'm going to have to see some very credible and convincing evidence before I do. <HR></BLOCKQUOTE> Thats cause you guys are looking in the wrong direction.Penetration is linked to projectile lenght not diameter, thats why no one uses these formulas any more.I've just finished working through the 2Lb & 17Lb APDS and German 75L24 , L48 & L70 APCBC ammo as well as the 88 Flak 18 & L71 APCBC ammo using projectile lenght , L/d value , ratio of tip to body diameter and tip hardness, and MV... and got within a few mm of the published vertical penetration data for 0-100m range.By using the empirical test results. This is far from conclusive and I'll have to do some more work to see if I can find more results to compare.