Conraire

ID:0056670 25/Apr/2017 APDS in game using incorrect Slope modifiers

Think it's as done as it's going to get. 

Vehicles Effected:  All vehicles that fire APDS Shot projectiles.  All game modes

A34 Comet I

A30 Challenger

A43 Black Prince

Centurion Mk 1

FV221 Caernarvon

Tank Medium Gun Charioteer Mk VII

Centurion Mk 3

Centurion M 10

Tank Heavy Gun Conqueror Mk 2

FV 4004 Conway

Strv 81

Chieftain Mk 3

STB-1

Type 74

Light Tank M41 SDF

T-54 Mod. 1949

T-54 Mod. 1951

T-62

T-10M

SU-122-54

Leopard 1

Leopard A1A1

Light Tank M41A1 Walker Bulldog

76mm Gun Tank T92

105mm Gun Tank M60

105mm Gun Tank M60A1


 

2: The issue is all APDS currently in the game, is packed into one set of incorrect slope modifiers.  The issue with this is, there are 3 different major design generations of APDS in game, 4 if you include the fin stabilized discarding sabot of the T-62..  These different generations of APDS, all have their own unique slope effects, due to differences in core design, which isn't modeled in game currently.

EGFb7qJ.jpgUMbLbRd.jpgepYCxly.jpgUdDUCze.jpgkseKFvm.jpgW10fOyP.jpgRwbGakl.jpgdyET0Gk.jpgutFszW3.jpg8c6dztg.jpgBUt7L5P.jpgdxQwo4p.jpgURjkwav.jpgoIzWMwc.jpgEuvqAEy.jpg


 

As can be seen, when you do the math, the current in game slope modifier for 30 from horizontal/60 degree's obliquity is 2.46-2.47 across the board.  This is obviously incorrect, especially for first generation APDS, in fact, this means Russian 3bm11, 7, and 8(first gen apds core designs) are all over performing greatly vs high obliquity plate, while at the same time under performing vs vertical. 


 

3:  The solution to fix the issue properly, is to divide the different APDS shots by core design generation.  The differences between the core generation designs will be illustrated below with cut away pictures of known APDS projectiles.  The differences will be pretty obvious when you see the pictures. 


 

The APDS Core Generations


 

First Generation APDS:

Sharp nose core

has very similar characteristics to HVAP. 

This is the APDS from World War 2 Ballistics

Which means great vs vertical plate, lackluster vs high obliquity.

From left to right: Shot APDS Mk1 for 17pdr and 77mm, 20pdr APDS Shot Mk3, 100mm APDS 3BM8, 122mm APDS 3BM11.

This group also includes 76mm M331A2, 120mm APDS L1, and 120mm T98 or T102 APDS, if they ever get added. They just aren't pictured.

17pdr_apds.jpg20pdr APDS Mk3100mm+bm-8+apds-t.JPG122mm_3BM11%20APDS%20Round_2.jpg1489834870-15822612-2187245141500623-413


 


 

Second Generation APDS:

Double conical semi blunt nose core

This if where things change drastically. 

Vertical plate performance is sacrificed to improve high obliquity plate performance when compared to first generation APDS.

This group included 105mm L28A1/M392, 105mm L36A1/M392A2, 105mm DM13

DSCF1102.jpg


 


 

Third Generation APDS:

Round nose design with narrower longer Core

Regains some vertical plate penetration performance, with improved performance vs slopes over second and first generation cores from the same caliber guns.

From Left to Right: 105mm L52/M728, 120mm TK APDS L15A5.  Currently these are the only members of the 3rd generation group L15A3 being whats in game. 

PWpqM7Ll.jpgl15a5_apds.jpg1489834913-15826306-2187248801500257-822


 


 

The Slope modifier problem


 

First Generation Sharp nose Core APDS, Should be using the slope modifiers from World War 2 ballistics. Unless domestic information is available for the shot.  And then the shot should have its own slope modifiers to make it correct. Though for the most part using World War 2 Ballistics slope modifiers for all first gen APDS would work as a blanket fix.

tHULAGZ.jpg kcgoOc8.jpg ZEWqscT.jpg

uw2PgLG.jpg


 

For example according to the equation from ww2 ballistics, slope modifiers for APDS should be as follows, or very close to them:

0°      = 0

30°    = 1.23

55°    = 2.74

60°    = 3.54

 

I'm going to use Numbers from Armament for Future Tanks or similar combat vehicles, as an example to show how close real world APDS testing comes to those modifiers, note there are some variances due to differing core diameters, etc.

mwUL6oT.jpg

From Document armament for future tanks or similar combat vehicles.

120mm T102 HVAPDS @ 4500ft/s or 1371m/s 23lb projectile, Sharp nose core(first generation), 75mm core diameter, approx 12lb core
Angle  1000yd    2000yd
         495mm     444mm
30°       406mm     365mm   Slope Mod = 1.22, 1.21
55°       155mm     139mm   Slope Mod = 3.19, 3.19
60°       137mm   ~123mm   Slope Mod = 3.61, 3.61

 

Using World War 2 Ballistics Slope Modifiers, it would look like this

Angle  1000yd    2000yd
         495mm     444mm
30°       402mm     360mm  
55°       180mm     162mm  
60°       139mm     125mm 


Here the only one that's off at both ranges, is the 55degree slope modifier.  Otherwise they all fall within .1 of the calculated modifier. 


 

14WT4gf.jpg

From Document armament for future tanks or similar combat vehicles. 

50mm Sharp nose core, 8.2lb projectile, approx 4.3lb core fired at 4125ft/s

76mm M331A2 HVAPDS-T @ 4125ft/s or 1257m/s
Angle      1000yd       2000yd
0/90°        261mm       231mm
30/60°      193mm       170mm     Slope Mod = 1.35, 1.35
55/35°        94mm         78mm     Slope Mod = 2.77, 2.96
60/30°        73mm         61mm     Slope Mod = 3.57, 3.78

 

The only one that's really different here at 1000yds is 30/60 with a modifier of 1.35, otherwise at the same range the slope modifiers fall within margin for error.  The oddities for this round from that document happen at 2000yds where 55 and 60 degree seem to jump off by a bit. 

 

Using World War 2 Ballistics Slope Modifiers, it would look like this, PB Estimated by the difference between 1000 and 2000yds.

Angle         P.B.      1000yd       2000yd
0/90°        291mm    261mm       231mm
30/60°      236mm    212mm       187mm
55/35°      106mm      95mm         84mm
60/30°        82mm      73mm         65mm

 

As another example of a round fitting first generation APDS Criteria, here is some information for 100mm 3bm8 from the D-10T gun. 

Ustyantsev Kolmakov Combat vehicles Uralvagonzavod T-54 T-55, is apparently the source of this.

PdpHst9.jpg

On 3/20/2017 at 8:03 PM, bigbobthewhiteWT said:

Source I don't know

 

So, it says basically,

 

by summer 1964 the firing range trials / tests of subcaliber round for D-10T were done (=passed), (the round has no name as of this date.).  In tests the APDS had a V0 of 1415m/s and a "straight shooting range" (no corrections needed) of 1660m on a 2m high target. At 1900-2000m penetration of 290mm at 0° and 80mm at 60° (also at this distance) It was officially accepted as 3B8 (typo, 3BM8) in 1967... and basically existed since late 1964.

 

Drawing shows a 412B by the way.

 

Just above the box, it says that HEAT-FS (non rotating) were developped from 1954. As we know the 3BK5 is 1961 official acceptance, so anything from 1955-56 is a given for small availability.

 

After the box, it says a demonstration of efficiency of this round (or rather inefficiency) was an Azeri T-55 shooting at an armenian T-72 (with no ERA) at 1000m in the turret and it didn't penetrate. (not sure why they mention this, it's pointless and the T-72 was made to be imune to this kinds of rounds frontally... 3BM8 was a M48-M60 killer in its design, not for anything above that.)

 

So for 100mm 3bm8 APDS, First Gen Core design, we have 290mm at 2000m at 0°, and 80mm at the same range at 60°.  This produces a slope modifier of 3.62, which is again within 0.1 of World War 2 Ballistics slope modifier for APDS.  3BM8 is one of those unique situations in game where it's over performing vs slopes, but greatly under performing vs vertical. 

 

Using World War 2 Ballistics Slope Modifiers, it would look like this, PB and 1000m Estimated by similarity to 76mm M331A2 APDS. Both use a 50mm core of similar mass and design, 3bm8 is fired at a higher velocity 1415m/s, compared to 1257m/s.

Angle         P.B.      1000m        2000m
0/90°        350mm    320mm       290mm
30/60°      284mm    260mm       235mm
55/35°      127mm    116mm       105mm
60/30°        98mm      90mm         82mm

 

Some outliers of the first gen type, which seem to have lower or higher than normal slope modifiers are:

3BM7

On 1/19/2016 at 3:42 PM, Choogleblitz said:

3BM7 (APDS-T)

Penetration:

300 mm @ 0° - 1,000 m - Soviet standard

100 mm @ 60° - 1,000 m - Soviet standard

 

270 mm @ 0° - 2,000 m - Soviet standard

  90 mm @ 60° - 2,000 m - Soviet standard

 

Sources:

Shirokorad AB - Encyclopedia of Russian artillery:

Middle Column for 122mm D-25TC

LWn4MdC.jpg?1

Which produces a slope modifier of 3.0, Below what WW2 ballistics predicts.

 

3BM11

On 1/19/2016 at 3:42 PM, Choogleblitz said:

3BM11 (APDS-T)

Penetration:

370 mm @ 0° - 1,000 m

140 mm @ 60° - 1,000 m

 

300 mm @ 0° - 2,000 m
115 mm @ 60° - 2,000 m

 

Sources:

Shirokorad AB - Encyclopedia of Russian artillery:

First Column for 122mm M-62T2C

LWn4MdC.jpg?1

This gives a slope modifier or 2.6-2.64, which is much lower than it should be for first generation apds.  Its possible that the vertical pen could be lower than it's suppose to due to differences in Russian Test plate and US Test Plate, which wouldn't effect 60degree's much but would have an effect on vertical plate. 

Using World War 2 Ballistic Slope modifier, the penetration would be:

Penetration:

495 mm @ 0° - 1,000 m

140 mm @ 60° - 1,000 m

 

407 mm @ 0° - 2,000 m
115 mm @ 60° - 2,000 m

 

Alternate source for 3bm11 Penetration at 2km is

Domestic Armoured Vehicles 1945-1965:

fPC5kLl.jpg

Which gives 320mm and 110mm respectively at 2km.  Which produces a 2.9 slope modifier. Again, lower than the 3.54 modifier, likely due to plate hardness.

Using World War 2 Ballistic Slope modifier, the penetration would be:

389 mm @ 0° - 2,000 m
110 mm @ 60° - 2,000 m

Likely much closer to what US Penetration Standard would give it.

 

A short bit on 120mm L1G APDS.  This also being a first generation round.  This is from the documents listed by @bellezza03

20131231_142341.jpg?w=700&h=

 

In the first paragraph about APDS it's comparing 120mm L1 apds to 120mm L15 apds.  It states that 120mm L1 penetrates 125mm @ 60 degree's at 1000yds, compared to L15's 150mm at the same angle and range. I know what sources around the internet are worth, but from multiple pages a figure of 446mm at 1000yds vs vertical plate is claimed.  Though I can't really use it as a source, it does give us a target value to go by.  I can try and order a copy of the firing trials and tables for the round to post as a supplemental, but that will cost me about $50, so it may take some time for that to happen. 

 

446/125 = 3.568 slope modifier.  Very close to WW2 Ballistics figure of 3.54.  Now of we take the published penetration results and apply ww2 ballistics slope modifiers we get:

 

1000yds

442mm @ 0°

359mm @ 30°

161mm @ 55°

125mm @ 60°

 

Regarding 20pdr APDS Mk3 and 17pdr APDS mk 1

penetration data at 30° degree angle ( 60° in game) source: Cromwell Cruiser Tanks, 1942-1950, David Fletcher & Richard C Harley, 2006

 

pkyTLve.jpg

In both cases 30degree obliquity / 60 degree in game is used to calculate Vertical which is used to calculate 55 and 60 degree obliquity

17pdr APDS Mk1 Fired at 1203m/s

 

               500yds        1000yds      1500yds      2000yds

0°           255mm          236mm        216mm        198mm

30°         208mm          192mm        176mm        161mm

55°           93mm           86mm           78mm          72mm

60°           72mm           66mm           61mm          55mm

uLHY9ip.jpg

You can see here how close the Numbers calculated via slope modifiers are to those listed in World War 2 ballistics at the same ranges.

 

20pdr APDS Mk3 Fired at 1430m/s

               500yds        1000yds      1500yds      2000yds

0°           362mm          340mm        319mm        298mm

30°         295mm          277mm        260mm        243mm

55°         132mm         124mm         116mm        108mm

60°         102mm           96mm           90mm          84mm

 

 

 

Second Generation,

Conical Blunt semi blunt nose APDS Should have its own set of slope modifiers.

The only current problem with that, is that solid information on the performance of these second generation rounds vs vertical plate is difficult to find. I do have Document requests filed with DTIC regarding M392A1 and A2 which should eventually shed some light on second Gen apds performance.  Temporary Solution for second generation APDS, would be to continue using current in game slope modifiers until Documentation is found and posted. 

 

 

Third Generation

Conical Round nose APDS,

Again should have it's own slope modifiers separate from first and second generation APDS. @bellezza03 has more documents on this than I do, along with the names of said documents.

Using 120mm L15A3 APDS performance. 

On 3/19/2017 at 11:13 AM, bellezza03 said:

New generation APDS with a new core, longer and with less width. Penetration charts from DEFE 15/1183 claims 150 mm at 60° at 1000 yards and 140 mm at 2000 yards. I have also a second source DEFE 15/1123 claiming the same values at 1000 yards. 4300 fps is speed of L15A3 at 1000 yards. Jane's also reports 355 mm of penetration at 1000 yards.

 

1464368924-l15-apds-versus-slope.png20131231_142507.jpgefV9cbM.jpg?1

 

From Janes Ammunition Handbook 2002.

 

yOapwhC.jpg

 

Taking the 355mm at 1000yds, and 150mm at 1000yds we get a slope modifier of 2.36 for third generation, round nose, APDS.

From what @bellezza03 posted above, I came up with the Numbers below for L15A3 based off documented vertical plate penetration combined with documented 60degree obliquity plate penetration.

0       yards: 377 mm/0°  160mm/60°

1000 yards: 355 mm/0°  150mm/60°

2000 yards: 330 mm/0°  140mm/60°

 

 

Also from Janes Ammunition handbook regarding 105mm L52 APDS. 

zCVHZfh.jpgs3Yy7jL.jpg

 

When We apply the above Slope modifier for Third Generation APDS to L52.  Which is of the same core design.  0m, 500m and 2000m penetration calculated based on the difference between 1000 and 1500m.

0m        332 mm/0°  140mm/60°

500m    306 mm/0°  129mm/60°

1000m: 280 mm/0°  118mm/60°

1500m  254 mm/0°  107mm/60°

2000m  228 mm/0°    96mm/60°

 

The 1500m Penetration number claimed in Janes, can be backed up by whats listed in Tradoc 1u RANGE AND LETHALITY OF U. S. AND SOVIET ANTI-ARMOR WEAPONS From Sept 1975, by that time L52/M728 was the standard apds round.  In this document, Mid range is considered to be 1500m.  10inches = 254mm

HUqAOOQ.jpg

 

As a secondary source for Vertical Penetration for M728/L52 there is "M60 vs T-62 Cold War Combatants 1956-92" by Lon Nordeen & David Isby.  PDF e-book ISBN: 978 1 84908 296 9

These numbers appear to be close estimates of whats listed in the above books.

zBOjSbj.jpg

M728 vertical Data from M60vsT62 book. with 2.36 modifier applied for 60obliquity.

Angle       500m      1000m     1500m         2000m
             300mm    275mm     250mm        225mm
60°           127mm    116mm     106mm          95mm

 

 

Summary

 

The Following Should become First Generation APDS or APDS Type 1, and use slope modifiers from World War 2 Ballistics. 

This would also give them closer to USN criteria Performance for Russian rounds, and their historical sourced penetration for most Early style  US and British APDS rounds.

17pdr and 77mm SVDS Mk 1

76mm M331A2 APDS-T

20pdr APDS Shot Mk3

100mm APDS-T 3BM8

120mm APDS-T Shot L1G

120mm APDS-T T98 (preemptive in case they add it to T34)

122mm APDS-T 3BM7

122mm APDS-T 3BM11

 

The Following should become Second Generation APDS, or APDS type 2.  These would continue using current 30/60° obliquity slope modifiers.

105mm DM13

105mm M392A2

105mm Shot L-28A1

 

And Last but not least, the Following should become Third Generation APDS, or APDS Type 3, using the 30/60° obliquity slope modifier based off L15A3 Performance

105mm M728

120mm Shot L15A3

Edited by Conraire
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Hi Conraire,

Thanks for the report.

 

I will wait for you to finish.

 

I will then read, investigate and get back to you shortly,

 

Cheers,

KotA

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I think it's about as done as I'm going to get it for now.  I'm still waiting on some information from DTIC.  And I'm also trying to get with @Listy, @bellezza03, @Choogleblitz, and other sources for more information.

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More addition to 1st Generation APDS

17 Pdr APDS

17 pdr Scheme shell scheme with "fatty" core and rounded ballistic cap. Then penetration table from WWII ballistic armor and gunnery.

Risultati immagini per 17 pdr APDS

Here we have a penetration chart found in british archieves by "The Chieftain" about 17 pdr Behaviour  that confirms 17 pdr APDS values from WW2 Ballistics armor and gunnery. Panther UFP defeated at 1150 yards ( 1 km). Doing 84X2,75 (55° Slope modifier) we have 231 mm. In accord to ww2 ballistic and gunnery tables. Also i have this piece of a vast report of US testing of Sherman firefly during winter at Fortknox. 1946

Risultati immagini per 17 pdr penetration chart
 
17 pdr APDS penetration table against armor at 30° from vertical.
17prpencomp_684x159.jpg

5kc2mdpvlag.jpg

So Penetration for  17 Pdr APDS is

                         0°             30°           60°

0       meters  275 mm   233 mm     78 mm

1000 meters  233 mm   193 mm     66 mm

2000 meters  194 mm   160 mm     55 mm

 

About L1G APDS for Conqueror Main armament

L1G APDS

  Hide contents

Same fatty core of 1st generation.

Now according to DEFE 15/1183 penetration is 125 mm at 60° at 1000 yards. Jane's Ammunition Handbook says 446 mm at 1000 yards which considering the 3.5X slope modifier is a value in perfect accord to official documentation. 

https://tankandafvnews.files.wordpress.com/2016/02/20131231_142341.jpg?w=700&h=

A complete penetration table would be like this

                       0°                 60°

0       yards 473 mm/0° 135 mm/60°

1000 yards 446 mm/0° 125 mm/60°

2000 yards 426 mm/0° 121 mm/60°

 

About 20 pdr APDS mkIII

20 pdr APDS mk III

  Hide contents

A 20 pdr mk III cutoff. Same fatty core, but now ballistic cap has changed being sharp. MKI instead has rounded ballistic cap like 17 pdr APDS

Risultati immagini per 20 pdr APDS mk3

penetration data at 30° degree angle ( 60° in game) source: Cromwell Cruiser Tanks, 1942-1950, David Fletcher & Richard C Harley, 2006

.eJwNycsNwyAMANBdGABbOATIBhnDIogghY_APVX

500yards=11.61inch

1000yards=10.91inch

1500yards=10.24inch

2000yards=9.56inch

 

So converting to the good olds centimeters ( 0°30° 60°)

500 yards:361 mm 294 mm 105 mm

1000yards:340mm 277 mm 97 mm

1500yards:319mm 260 mm 91 mm

2000yards:297mm 243 mm 85 mm

 

Edited by bellezza03
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Hi Conraire, All contributors,

                  I will need some more references please.   All references need to be concise and clearly marked if you want them in the report.  Can each contributor go through the report and ensure that what ever they have added is clearly referenced according to the guidelines. 

 

For Instance:

All the APDS round pictures at the top need to be identified and referenced.

"From Document armament for future tanks or similar combat vehicles."    I will need more information about this document

The Developers need to be able to read this document.  I have blown it up to read and find it very difficult to read.  Can we get a scan of each page that is readable please.  Also I need to know what the document is.

20131231_142341.jpg

 

The above are just examples there are more inclusions that require complete references.

 

ALL documents and evidence must comply with the referencing standards stated in the Guidelines.  These are the basic referencing standards used in the commercial, industrial and educational sectors.

 

Can I draw the attention of all to the guidelines for making a Historical Issues Report HERE  -  Please ensure your reports comply with these guidelines.

Can I draw your particular attention to point 3 of the above link please;
3. A detailed description of the fix you suggest. Provide sources including references that underline your position.
    *Please be reminded that Wikipedia or other private Websites are generally not considered as reliable sources.
   The required number of sources requires depends on the type of source presented:
    User Manual / Repair Manual / Factory Manual etc (Flight/Pilot/Maintenance Manuals Engineering Drawings etc) - Historically acknowledged reference sources - single source is required.
    Reference works (collections of vehicles) Biographies, Books, "expert" opinion publications, websites etc - at least two unrelated sources required. *
Please ensure the references have:  Report/Document Type, Report/Document Name, Author, Date, ISBN/ISSN, relevant Pg No's etc - so our Historical consultant can review and check the accuracy of those documents against the substantial Gaijin Historical Database and Reference Sources.
Please provide scans of all pages referenced and a scan of the front cover of publication/book.  
For Web sources. please provide the link to the actual relevant section or document.  If this is not possible and only higher links can be referenced then please provide page or title information to locate the relevant reference.
Photographs need to be fully referenced.

 

Thanks

 

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Hello!
         Thank you for your help improving the game.  

 

Your information has been forwarded to the developers and the tracking number is: ID:0056670   

This thread will remain unlocked for one week (7 days) so that anyone with additional information\evidence\examples will have a place to post.  

 

After this time the report will remain active but will be archived.

It will also serve as a place where the developers will post questions for you to answer so please keep up to date here.

 

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Finally have some information on second generation APDS.... The vertical plate numbers seem fairly accurate, especially since I've seen the same for L52/M728 before.  As far as I can tell the numbers labeled 60degrees are most likely actually 30degree's obliquity values, and not 60degree's obliquity.  So it would appear that L28/M392/DM13 second generation APDS don't lose as much vertical penetration as I'd originally thought.  So far the only 60degree obliquity numbers for L28/M392/DM13 I have are 127mm at 4606ft/s which is approximately 1000m, given a muzzle velocity of 4800-4850ft/s.  I won't know the exact range until I get ahold of the firing tables for the 105mm M68 gun here in a couple weeks. 

 

So for now, 348mm / 127mm = 2.74 slope effect for second generation apds at 60degree obliquity.  and 1.375 for 30degree obliquity. 

 

NII Stali book "Защита"/Defence(or Armour),

zrDTGl1.jpg

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Information Added

 

Archived

 

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