Vanir Ausf B Posted June 5, 2014 Share Posted June 5, 2014 It's not just possible. It's almost a certainty when you factor in the exact properties of the impacting projectile. As mentioned earlier, the 76.2mm shell vastly overmatches a 20mm thick plate (thickness/diameter ratio = .2625). When struck by 76.2mm APBC, a 20mm plate angled at 70.5° from vertical resists equivalent to 26.9mm. Factor in 95% armor quality for the Pz IV H (per CMBB) and the armor resistance is 25.5mm. EDIT: Wrong value. See below. 0 Quote Link to comment Share on other sites More sharing options...
Kauz Posted June 5, 2014 Author Share Posted June 5, 2014 It's not just possible. It's almost a certainty when you factor in the exact properties of the impacting projectile. As mentioned earlier, the 76.2mm shell vastly overmatches a 20mm thick plate (thickness/diameter ratio = .2625). When struck by 76.2mm APBC, a 20mm plate angled at 70.5° from vertical resists equivalent to 26.9mm. Factor in 95% armor quality for the Pz IV H (per CMBB) and the armor resistance is 25.5mm. Could you specify for me how you get the 26.9mm ? 0 Quote Link to comment Share on other sites More sharing options...
Vanir Ausf B Posted June 5, 2014 Share Posted June 5, 2014 T x F x (T/D)^G T= armor thickness T/D= thickness/diameter ratio (armor thickness/projectile diameter) A= angle of impact F=2.71828^(0.03723 x 1.06033^A) G= -3.3667 + 0.07411 x A 0 Quote Link to comment Share on other sites More sharing options...
Kauz Posted June 5, 2014 Author Share Posted June 5, 2014 T x F x (T/D)^G T= armor thickness T/D= thickness/diameter ratio (armor thickness/projectile diameter) A= angle of impact F=2.71828^(0.03723 x 1.06033^A) G= -3.3667 + 0.07411 x A source? thx 0 Quote Link to comment Share on other sites More sharing options...
Vanir Ausf B Posted June 5, 2014 Share Posted June 5, 2014 GAA! I totally boned the math. Equivalent armor resistance is actually 16.9mm, or 16.0 with 95% armor quality. source? thx World War II Ballistics: Armor and Gunnery (second edition) by Lorrin Bird and Robert Livingston, pgs 20-21 0 Quote Link to comment Share on other sites More sharing options...
Kauz Posted June 5, 2014 Author Share Posted June 5, 2014 T x F x (T/D)^G T= armor thickness T/D= thickness/diameter ratio (armor thickness/projectile diameter) A= angle of impact F=2.71828^(0.03723 x 1.06033^A) G= -3.3667 + 0.07411 x A something wrong? T=20mm T/D= 20mm/76,2mm=0,26247 A=70.5° F=2,71828^2,31466=10,12147 G= -3.3667 + 5,224755 = 1,858055 T x F x (T/D)^G = 20mm x 10,12147 x 0,26247^1,858055 = 20 x 10,12147 x 0,08329 = 16,86 mm 16,86mm is not your 26,9mm.... Did i something wrong? EDIT: You answered while i was writing this. Thank you for the information ! 0 Quote Link to comment Share on other sites More sharing options...
Vanir Ausf B Posted June 5, 2014 Share Posted June 5, 2014 Alternatively: Slope Effect at Angle = a x (T/D)^b For APBC @ 70°: a = 9.477, b=1.8152 9.477 x (.2625)^1.8152 = .836 .836 x 20mm = 16.7mm (WW II Ballistics pg 118) 0 Quote Link to comment Share on other sites More sharing options...
Kauz Posted June 5, 2014 Author Share Posted June 5, 2014 Alternatively: Slope Effect at Angle = a x (T/D)^b For APBC @ 70°: a = 9.477, b=1.8152 9.477 x (.2625)^1.8152 = .836 .836 x 20mm = 16.7mm (WW II Ballistics pg 118) Thanks again... !!! 0 Quote Link to comment Share on other sites More sharing options...
Vanir Ausf B Posted June 5, 2014 Share Posted June 5, 2014 Note that the thickness and angle of that plate is not consistent for all Pz IV models. On the ausf G it is 25mm thick @ 73°, which translates to equivalent resistance of 33.8mm (T/D = .3281 and 71.5° angle vs. 76.2mm APBC). So you can see how much the overmatching projectile affects the resistance where a 5mm increase in armor thickness doubles the effective resistance. But it will still penetrate 0 Quote Link to comment Share on other sites More sharing options...
Kauz Posted June 5, 2014 Author Share Posted June 5, 2014 Note that the thickness and angle of that plate is not consistent for all Pz IV models. On the ausf G it is 25mm thick @ 73°, which translates to equivalent resistance of 33.8mm (T/D = .3281 and 71.5° angle vs. 76.2mm APBC). So you can see how much the overmatching projectile affects the resistance where a 5mm increase in armor thickness doubles the effective resistance. But it will still penetrate I heard about the overmatching issue... Could not imagine that it can have such a tremendous effect... thank you again.... Do you have a hard copy of the book or a scan? 0 Quote Link to comment Share on other sites More sharing options...
76mm Posted June 6, 2014 Share Posted June 6, 2014 Question for all of you penetration grogs: one issue which has not come up is elevation differential, if any, eg, whether the T34 had an elevation advantage over the PIV--presumably that would also affect the penetration calculations by changing the angle of impact? 0 Quote Link to comment Share on other sites More sharing options...
Oddball_E8 Posted June 6, 2014 Share Posted June 6, 2014 Admittedly, I'm only skimming through all this since I can't be bothered to do math at 5 am when I just woke up, but it seems to me that people are still not taking into effect that angle of trajectory for the shell. It's not hitting from straight ahead, it is hitting from slightly above due to the 1500m range trajectory. Thus negating alot of that 70-75 degree angle you are using. 0 Quote Link to comment Share on other sites More sharing options...
Kieme(ITA) Posted June 6, 2014 Share Posted June 6, 2014 Don't worry Odd, I am sure there's a magic formula to show how a 76mm round "ballisticly" behaves, there must be somewhere the round weight, gun's muzzle velocity, plus a lot of data such as pressure on ground level etc. Enjoy 0 Quote Link to comment Share on other sites More sharing options...
Vanir Ausf B Posted June 6, 2014 Share Posted June 6, 2014 Admittedly, I'm only skimming through all this since I can't be bothered to do math at 5 am when I just woke up, but it seems to me that people are still not taking into effect that angle of trajectory for the shell. It's not hitting from straight ahead, it is hitting from slightly above due to the 1500m range trajectory. Thus negating alot of that 70-75 degree angle you are using. As previously mentioned, it does not negate "alot" of the angle of impact. And that small amount has been factored in. 0 Quote Link to comment Share on other sites More sharing options...
Vanir Ausf B Posted June 6, 2014 Share Posted June 6, 2014 Question for all of you penetration grogs: one issue which has not come up is elevation differential, if any, eg, whether the T34 had an elevation advantage over the PIV--presumably that would also affect the penetration calculations by changing the angle of impact? Sure it would. But only the OP would know. 0 Quote Link to comment Share on other sites More sharing options...
Oddball_E8 Posted June 6, 2014 Share Posted June 6, 2014 As previously mentioned, it does not negate "alot" of the angle of impact. And that small amount has been factored in. Where was this mentioned? I must have missed it? (and when playing CMRT at those distances, it does seem like it IS a significant angle actually) EDIT: Nevermind, found it: The angle of decent for Soviet 76mm at 1500 meters would be around 1.5 degrees, so that is not really a major factor. The problem with single events like this is that we don't know for sure if CMx2 models weak point penetrations. We do know that there is no weak point penetration hit text so the only way to find out if there is a problem is further testing. But if you look at the video I've uploade you'll see what appears to be far more than 1.5 degrees angle on that shell... 0 Quote Link to comment Share on other sites More sharing options...
Oddball_E8 Posted June 6, 2014 Share Posted June 6, 2014 Just made a quick movie to show what I mean by "significant angle". Just a quick setup in CMRT with a T-34 firing on a panzer IV (G, but for these purposes it doesn't matter) at exactly 1500 meters. You'll see that the angle is rather large after all (not as visible from the PzIV's view, but very visible from the T-34's view). Here: Ps. The kill shot was almost exactly where the OP had his. EDIT: It is interesting to note that at 1500 meters, the ELITE T-34 took more than a minute on average to spot, or rather re-spot, the tank it had already fired upon before. With no terrain around and no other significant targets. 0 Quote Link to comment Share on other sites More sharing options...
Vanir Ausf B Posted June 6, 2014 Share Posted June 6, 2014 Where was this mentioned? I must have missed it? Page 1: The angle of decent for Soviet 76mm at 1500 meters would be around 1.5 degrees, so that is not really a major factor. Note that this is an estimate. I used the number for US 75mm APCBC since I had that number handy and it is ballistically similar enough to Soviet 76mm that the difference will not be off by more than a few tenths of a degree. If anything the 76mm may have a slightly flatter trajectory as it has a higher muzzle velocity. 0 Quote Link to comment Share on other sites More sharing options...
Oddball_E8 Posted June 6, 2014 Share Posted June 6, 2014 Page 1: Note that this is an estimate. I used the number for US 75mm APCBC since I had that number handy and it is ballistically similar enough to Soviet 76mm that the difference will not be off by more than a few tenths of a degree. If anything the 76mm may have a slightly flatter trajectory as it has a higher muzzle velocity. For the F-34 the muzzle velocity is 655m/s from what I remember. BTW. did you miss my other post and my video? 0 Quote Link to comment Share on other sites More sharing options...
Vanir Ausf B Posted June 6, 2014 Share Posted June 6, 2014 For the F-34 the muzzle velocity is 655m/s from what I remember. Yes. And the muzzle velocity of the US 75mm M3 is 619m/s. BTW. did you miss my other post and my video? I watched the first half. You can't measure angle using that video but it does not appear to large at all to my eyes. 0 Quote Link to comment Share on other sites More sharing options...
Kauz Posted June 6, 2014 Author Share Posted June 6, 2014 -Interessting was that the kill shot seems to be closely the same like my kill. -Further i ask myself if the hit decals are exact because someone said they are not. -For me (in my game) the impact angle looked not small either....but it is hard to measure....better calculate.... nevertheless it seems not to be important for the outcome due to Vanir´s mentioned reference of the extreme bad overmatch-behaviour of 20mm plates. I really thought ~70° is such a hard match for a round.....not only geometric wise....because of the less effectivity of the round at big angles too (cause by diverted impluse and misforming of the shell). But these 20mm destroy the whole effect -Would be interessting to know from where Bafflefront got his ballistic/trajectory formula for all weapons. -BTW.: I always read for the F-34 a start velocity of 680 m/sec. 0 Quote Link to comment Share on other sites More sharing options...
poesel Posted June 6, 2014 Share Posted June 6, 2014 -Further i ask myself if the hit decals are exact because someone said they are not. IIRC Steve said they are. 0 Quote Link to comment Share on other sites More sharing options...
Oddball_E8 Posted June 6, 2014 Share Posted June 6, 2014 -BTW.: I always read for the F-34 a start velocity of 680 m/sec. It seems the HE shells have a velocity of that. Odd that the AP shells have a slower velocity overall :/ (of course, the APCR has 965). On the other hand, I just used wikipedia as a quickie source (blasphemy, I know) 0 Quote Link to comment Share on other sites More sharing options...
Amizaur Posted June 7, 2014 Share Posted June 7, 2014 Adding to discussion - the final angle of trajectory for a 76mm APBC shell fired from ZIS-5 gun at range of 1500m is minus 22 mils so about minus 1,32 deg (data from Russian ballistic tables). 0 Quote Link to comment Share on other sites More sharing options...
Kauz Posted June 9, 2014 Author Share Posted June 9, 2014 T x F x (T/D)^G T= armor thickness T/D= thickness/diameter ratio (armor thickness/projectile diameter) A= angle of impact F=2.71828^(0.03723 x 1.06033^A) G= -3.3667 + 0.07411 x A Hello Vanir, would like to get further information about the formula..... The formula has obviously limitations......... you may only be allowed to use this formula under special conditions. Why do i think that? you may ask....here comes the answer: For example: Try to use a 200 mm thick armor plate against this 76,2 mm round and tell me what the formula calculates as result. Here the results: at impact-angle of: 0°= 8,06mm :eek: 10°=16,97mm 20°= 36,6mm 30°= 82,34mm 40°=199,91mm 50°= 556,56mm 60°=1981,59mm 70°=10974,68mm 80°=134420,36mm 89,9°= 6520086,52 Sorry...but the Elefants should then have died like flys when they got shot by T-34/76 tanks and only had an equivalent armorprotection of 8-16mm steel instead of 200mm.... 0 Quote Link to comment Share on other sites More sharing options...
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