APDS SLOPE EFFECTS

[rexford]

If you go to

http://www.britwar.co.uk/salts/salt6.htm

do a search, and then open up the first address, there is a massive amount of WW II penetration data.. Close to the bottom is APDS slope multipliers at 30° and 60°, and CM underestimates APDS slope effects by quite a bit.

CM uses about 3 at 60°, the salts site has 3.53 at 60°. Tungsten was very brittle (and very hard, which often is associated with brittle behavior, like glass sheets), and be impacted more by angle than steel.

CM appears to underestimate the resistance of Panther and Tiger II armor, and the need to revise slope figures should be examined.

Tungsten slope effects should be substantially higher than AP or APCBC, as a general rule. However, at T/D=1 and 60°, AP slope effect is 4.00 compared to 3.00 for APCBC and 3.54 for APDS, so the general use has to be used with care. But how many steel AP rounds can penetrate 4 times their diameter without shatter?

We would note that the 60° sloe effect for U.S. HVAP is about 4.3 and much higher than APDS, which might be due to the carrier, nose shape or cap.

[rexford]

The search on the salts site is for "penetration". First site that shows up is the one to go to.

[Guest Big Time Software]

We've already stated that there's a bug in v1.1 concerning the tungsten slope modifiers. It will be fixed in the next patch.

Charles

[Panther131]

Now thats what I call good research.

Thanks rexford.

BTS...I probably should e-mail you. I did not mean to be out of hand when posting my arguments against armor point allocations in 1.1 So if I was out of hand, I apologize. I do not think I stepped out of bounds but I may have leaned in that direction

All in all, I was just trying to clarify the reasons given for change. I wanted to understand it more then I did and that is why I asked so many questions. I too am retiring from (I feel that this is wrong...) with out any further evidence to back up. I hope you all forgive me if I was out of hand.

Thanks to rexford, I now know how to present a case to BTS for proposed change. Thanks rexford, and thanks BTS for one of the best games ever made.

My hats off to you.

[Paul Lakowski]

Its also evident from the data that the amount the projectile turns changes with range , probably due to the arc of the projectile. I'm currently looking at a paper that shows different results for sloped impact from shot to shot suggesting that the spinning of the projectile plays a role but in some cases the projectile shattered at 45° in other cases it didn't and these are Tungsten Alloy Vs aluminum [ classic 'elastic plastic' projectile plate interaction].

My believe is that nose shape plays a role in this slanted impact/shatter situation. Heres some data for steel AP with tungsten carbide core vs slant RHA.

3.6:1 L/d steel 590BHN ogive 4.6 CRH with a Tungsten core @ 600-1500m/s Vs 255-295BHN plate @increasing angle , results = P/L value..... Int.J.Impact Engng Vol-22,pp 100-381 ;[pp172]

<PRE>

0° 20° 30° 1.36

1500m/s 1.0 0-.95 0.91

1400m/s 1.54 1.1 0.91 0.82 1.66

1300m/s 1.45 1.11 0.77 0.73 1.64

1200m/s 1.27 1.06 0.73 0.64 1.55

1100m/s 1.18 1.07 0.91 0.54 1.58

1000m/s 1.04 1.04 0.79 0.5 1.52

900m/s 0.95 1.05 0.73 0.59 1.53

800m/s 0.82 1.03 0.59 0.41 1.52

700m/s 0.68 0. 97 0.45 0.32 1.43

600m/s 0.54 0.9 0.36 0.18 1.32

</PRE>

The peak values [ highlighted] are the shatter zone or transitional velocity.The 24.4 caliber HVAP shot is ~ 6.2 mm

diameter and.22mm long. Result is in P/L values.At vertical the P/L of WC-St = 1.21 xV - In of L/d x 0.15 x sharpness =

[This message has been edited by Paul Lakowski (edited 01-22-2001).]

[rexford]

Since tungsten core (HVAP) penetration tests by America (and others) were at a constant close range and varied velocity through powder charge, range effects would not show up during firing tests at simulated range in meters.

U.S. tests for 76 and 90 HVAP generally show same slope effects with changes in velocity, only great variation is 90 HVAP at 55°, which might have been due to other factors (45° and lower angle hits had constant slope modifiers as velocity varied).

Thing about APDS slope effect is that it is alot lower than other tungsten core rounds. But it also would be alot higher when the sabot stuck, which would also destroy accuracy.

So inaccurate APDS also had bad or no penetration. This should be a part of CM, the inconsistency of APDS. As noted before in my posts. Jentz states that APDS "was not particularly accurate".

Irregular APDS is all we ask. Make it miss Panthers and Tiger II's at 200 yards, and bounce off PzKpfw II's when it does land on something. Not all the time, maybe half.

And don't forget the cracked Panther glacis after 17 pounder hits, this can be shown on the little tanks.

And how about Panther armor quality that only penalizes the glacis.

And....................

Good night.

[Dan Robertson]

I discovered the site a few months ago. I has plenty of data but a great deal of it is conflicting.

However I found the comentaries on each entry usually picked this up. What was also interesting was the reports to shafe at the end of it about the 17pdr and 77mm verses the tiger.

I took a look at some of the data and got a slope modifier of

cos 60 ^(2/1.1)

as the modifier for the APDS.

However the German 88 APCR seems to have a modifer

cos 60 ^(2/1.4)

I think this may be wrong.

It is possible that these figures were generated by calcualtion.

BTW

what are the slope effect on the German

75/48

75/70

88/71

APBCHE that is.

[Paul Lakowski]

Originally posted by Dan Robertson:

BTW

what are the slope effect on the German

75/48

75/70

88/71

APBCHE that is.

1951 WO 291/1143, "Effectiveness of British and Russian tanks."

Penetration in millimetres, ranges in yards:

<PRE>

Weapon Range 0º 30º 0.866 60º 0.5

77mm APCBC 600 145 115 ^ 1.6 52 ^ 1.47

1000 136 108 ^ 1.5 48 ^ 1.5

1500 124 100 ^ 1.5 45 ^ 1.48

17 pdr APCBC 600 172 136 ^ 1.6 62 ^ 1.46

1000 162 128 ^ 1.6 58 ^ 1.45

1500 150 119 ^ 1.6 55 ^ 1.45

17 pdr APDS 600 248 200 ^ 1.5 70 ^ 1.8

1000 232 188 ^ 1.4 65 ^ 1.8

1500 213 172 ^ 1.4 60 ^ 1.8

85mm APCBC 600 137 110 ^ 1.5 49 ^ 1.5

1000 128 103 ^ 1.5 46 ^ 1.48

1500 118 95 ^ 1.5 43 ^ 1.46

{from Russian 600 110 88 ^ 1.55 39 ^ 1.5

range tables) 1500 96 76 ^ 1.6 35 ^ 1.48

Weapon Range 0º 30º 0.866 60º 0.5

20 pdr APDS Mk 1 600 300 240 ^ 1.55 80 ^ 1.9

1000 280 225 ^ 1.5 75 ^ 1.9

1500 260 210 ^ 1.5 67 ^ 1.95

122mm APCBC 600 203 162 ^ 1.55 74 ^ 1.5

1000 193 153 ^ 1.6 70 ^ 1.47

1500 182 145 ^ 1.47 66 ^ 1.47

(from Russian 600 149 118 ^ 1.6 53 ^ 1.5

range tables) 1500 130 104 ^ 1.55 47 ^ 1.47

@ 30° @ 45° @ 60°

90mm APC 700- 750m/s 0.866 ^1.45 0.707 ^ 1.75 0.5 ^ 1.34

90mm HVAP 1000m/s 0.866 ^ 1.7 0.707 ^ 2.2 0.5 ^ 2.4

By comparison modern 90mm & 105mm ammo is ......

Angle & COS 10° 0.98 30° 0.866 45° 0.707 60° 0.5

AP 0.95 ^ 2 0.77 ^ 1.8 0.56 ^ 1.6 0.4 ^ 1.3

HVAP 0.97 ^ 1.5 0.8 ^ 1.5 0.54 ^ 1.75 0.37 ^ 1.43

APDS 0.98 ^ 1.0 0.806 ^ 1.5 0.61 ^ 1.4 0.47 ^ 1.1

HEAT 0.98 ^ 1.0 0.877 ^ 0.9 0.73 ^ 0.9 0.51 ^ 0.95

</PRE>

[This message has been edited by Paul Lakowski (edited 01-23-2001).]

[Herr Oberst]

Originally posted by Paul Lakowski:

1951 WO 291/1143, "Effectiveness of British and Russian tanks."

Penetration in millimetres, ranges in yards:

So much for work getting in the way...

<table cellpadding=2 cellspacing=2 border=1>

<tr>

<td>Weapon</td>

<td>Range</td>

<td>0 deg</td>

<td>30 deg</td>

<td>0.866</td>

<td>60 deg</td>

<td>0.5</td>

</tr>

<tr>

<td>77mm APCBC</td>

<td>600</td>

<td>145</td>

<td>115</td>

<td>1.6</td>

<td>52</td>

<td>1.47</td>

</tr>

<tr>

<td> </td>

<td>1000</td>

<td>136</td>

<td>108</td>

<td>1.5</td>

<td>48</td>

<td>1.5</td>

</tr>

<tr>

<td> </td>

<td>1500</td>

<td>124</td>

<td>100</td>

<td>1.5</td>

<td>45</td>

<td>1.48</td>

</tr>

<tr>

<td>17 pdr APCBC</td>

<td>600</td>

<td>172</td>

<td>136</td>

<td>1.6</td>

<td>62</td>

<td>1.46</td>

</tr>

<tr>

<td> </td>

<td>1000</td>

<td>162</td>

<td>128</td>

<td>1.6</td>

<td>58</td>

<td>1.45</td>

</tr>

<tr>

<td> </td>

<td>1500</td>

<td>150</td>

<td>119</td>

<td>1.6</td>

<td>55</td>

<td>1.45</td>

</tr>

<tr>

<td>17 pdr APDS</td>

<td>600</td>

<td>248</td>

<td>200</td>

<td>1.5</td>

<td>70</td>

<td>1.8</td>

</tr>

<tr>

<td> </td>

<td>1000</td>

<td>232</td>

<td>188</td>

<td>1.4</td>

<td>65</td>

<td>1.8</td>

</tr>

<tr>

<td> </td>

<td>1500</td>

<td>213</td>

<td>172</td>

<td>1.4</td>

<td>60</td>

<td>1.8</td>

</tr>

<tr>

<td>85mm APCBC</td>

<td>600</td>

<td>137</td>

<td>110</td>

<td>1.5</td>

<td>49</td>

<td>1.5</td>

</tr>

<tr>

<td> </td>

<td>1000</td>

<td>128</td>

<td>103</td>

<td>1.5</td>

<td>46</td>

<td>1.48</td>

</tr>

<tr>

<td> </td>

<td>1500</td>

<td>118</td>

<td>95</td>

<td>1.5</td>

<td>43</td>

<td>1.46</td>

</tr>

<tr>

<td>Russian Data</td>

<td>600</td>

<td>110</td>

<td>88</td>

<td>1.55</td>

<td>39</td>

<td>1.5</td>

</tr>

<tr>

<td> </td>

<td>1500</td>

<td>96</td>

<td>76</td>

<td>1.6</td>

<td>35</td>

<td>1.48</td>

</tr>

</table>

More later I hope...

------------------

To the last I grapple with thee; from hell's heart I stab at thee; for hate's sake I spit my last breath at thee...

[This message has been edited by Herr Oberst (edited 01-23-2001).]