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Rptd 20/Feb/2018 Incorrect model for AMX-30's "Obus G" HEAT shell


Hello,

 

Full name of the vehicles affected

AMX-30 and AMX-30B, and in particular, their Obus G HEAT shells. All game modes (AB/RB/SB).

Detailed description of the problem

The Obus G HEAT shell of the AMX-30 is currently badly modeled and is in particular using a damage model which does not at all render justice to what was at the time considered as the best heat shell.

Here, I provide 3 references (listed below and referred as A, B, and C) describing the working principle and the unique design of Obus G, and its performance.

Heat shells are classically stabilized by their rotation (rifled guns; like on the AMX-30) but which would diminish their damaging power (the spin would cause spalling to the jet of the shaped charge). The Obus G shell solves this problem by having the outer part of the shell rotate (stabilizing effect), while the internal charge mounted on ball bearings within the spinning projectile body would only rotate very slowly (typically 20-30 rotations/min [A]), hence retaining its full damaging power [A, B, C]. Therefore, like HEAT-FS shells, Obus G is stabilized for accuracy, and its shaped charge, barely spinning, retains its full capability.

 

In fact, the Obus G, with its conservative penetration of 360mm (see [A] and tests showing that it can easily penetrate 400 mm of armor steel [B, C]) had a better long-range accuracy than US HEAT and HEAT-FS shells (more sensitive to crosswind) and many other NATO shells [A, B, C], and was capable to go through several types of obstacles without exploding [B, C] (in game, it is currently stopped by foliage…).

The Obus G was hence universally recognized as an excellent and very precise HEAT shell (and “represented the almost ideal tank gun ammunition” [A]), but its design was ultimately abandoned due to its insane cost and to the increasing relevance of APDS(FS) to fight the most modern tanks [A].

 

The French War Thunder DEVBLOG describes Obus G as a “standard HEAT shell” while the English version speaks of  “a base HEAT shell”. By now, it should be clear that the Obus G is definitely not a standard HEAT shell and hence cannot be modeled using the same damage model as the HEAT shells from the 40s’. Right now, the paradox is that the AMX-30, relying only on its badly modeled Obus G shells, is the worst French tank in the BR 7.0-7.7 range, whereas it is also the most modern tank at this BR…

 

Here is an illustrative video (1 M60 and 5 AMX-30 sequences; see full description on YouTube)

2018_02_09_20_48_51__14916.clog2018_02_09_20_48_51__14916.clog
 

Description of the fix I suggest

I understand that Gaijin will probably not build a special damage model for one type of shell (but who knows?). The simple solution I propose would be to give Obus G the same properties as a (good) HEAT-FS shell, with a typical 360-400mm penetration ability, a better long-range accuracy, and a weaker sensitivity to obstacles, putting it at least at par with the HEAT-FS of the T-54 (1951), a tank built 20 years before the AMX-30 (1972)... Again, like HEAT-FS shells, Obus G is (better) stabilized for accuracy, and its shaped charge, barely spinning, retains its full damaging capability.

 

References

A. Tanks: 100 years of evolution (R. M. Ogorkiewicz, 2015, Osprey Publishing; ISBN-10: 1472806700; relevant pages: 189, 191, 209, 256); I have copied the relevant pages from Amazon “look inside” (kindle edition; but I give the page numbers of the hardcover edition), but I guess Gaijin could actually buy it if it has any doubt. These pages were found by researching “Obus” in the book. This source describes the design and working principle of the Obus G, its general performance, and in particular, its better long-range accuracy compared to US HEAT and HEAT-FS.
See also AMX-30 Battle Tank (also included below) by the same author (full text
here; see in particular p. 8 and 10) published as AFV Weapons Profiles #63. This source addresses in slightly more details the same points as the previous reference (principle, accuracy, damaging power, cost…), and mentions a 360-400mm penetration for Obus G and that this shell “represented the almost ideal tank gun ammunition”. Far from the case, in game…

Spoiler

Tanks: 100 years of evolution

REF-A1.jpg.4e7da5c688c1ba1fe452a0406d8a3

 

REF-A2.jpg.494a34dbc66f2cae8d6e96d422219

 

AMX-30 Battle Tank (AFV Weapons Profile #63)

page 8 - the relevant part starts at the "Gun and ammunition" section and continues in the first column of the next page

REF-A3.thumb.jpg.aaf143603120c11591468d7

 

 

B. AMX 30 France’s Main Battle Tank by General Jean Marzloff (he commanded the French tanker training center from 1963 to 1965): International Defense Review (2/1971; p. 110-113); the 4 pages are available on https://tankandafvnews.com/2015/04/06/amx-30-articles/; a general presentation of AMX-30 and its Obus G.

Spoiler

REF-B1.thumb.jpg.05ff433a06c8536084e6489

REF-B2.thumb.jpg.605df82ab17e20ce924dba8

 

 

C. AMX 30 Firepower – The Obus G HEAT round by Colonel Jean Périn (1972): International Defense Review (1/1972; p. 162-165); the 4 pages are available on https://tankandafvnews.com/2015/04/06/amx-30-articles/; this article explains in details the working principle of Obus G and presents the results of several tests showing 400mm of armor penetration, its immunity to light (and not so light) obstacles, and comments on test showing superiority to HEAT-FS at long range.

Spoiler

REF-C1.thumb.jpg.2c90da7289a34598b2dafd6

 

REF-C2.thumb.jpg.cd39a0b0617dafead7a2ceb

 

 

Edited by No_Camping
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  • KnightoftheAbyss changed the title to [1.75.0.180] Incorrect model for AMX-30's "Obus G" HEAT shell

Hi,

   Thanks for the report.

 

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

 

Cheers,

KotA

 

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As an aside comment, here is some biographical information on General Jean Marzloff (author of source B)

 

Jean Marzloff was born on 8th August 1906 in Brest and died on 22nd July 1996 in Saint-Denis-de-Palin.
He studied at the main French officer military academy of Saint-Cyr between 1928 and 1930 (his class was named after Marshall Foch)

 

He commanded the 8e régiment de hussards between 1955 and 1956 before commanding and overseeing the reformation of the 5e régiment de spahis in 1956 (he was a lieutenant-colonel at the time).

 

Before commanding the École d'application de l'arme blindée et cavalerie (EAABC; tanker training center) between 1963 and 1965, he was the first commander of the 11eme division légère d'intervention (DLI; light intervention division; in Balma near Toulouse where I live) between 1961 and 1963. There, General Marzloff decided in 1961 the creation of the Centre d'entraînement commando in Givet, the first French commando training center.


He ended his career as a 4 stars general.

 

 

Edited by No_Camping
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Hi
  Thank you for your interest and help improving the game.  

 

Your information has been forwarded to the developers for their consideration.  

 

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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  • KnightoftheAbyss changed the title to Rptd 20/Feb/2018 Incorrect model for AMX-30's "Obus G" HEAT shell
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