We’re talking about details of the adjusted APDS penetration values for hard alloy and tungsten alloy penetrators that we will introduce into the game in the Sky Guardians update.
In developing the game, we are trying to bring the parameters of shells of vehicles in the game to become more and more authentic. Thus in the Sky Guardians update we have transferred the calculation of armor penetration values for non-feathered armor-piercing sub-caliber discard sabot shells (APDS) to the modified Jacob De Marr formula. The coefficients were selected for different designs of such rounds in order to best match the known documents and known terminal performance results.
It is necessary to note the peculiarity of the influence of the design of the armor-piercing nose penetrative pad and the material of the penetrator. The use of a hard-alloy core made of tungsten carbide alloys makes it possible under optimal conditions to pierce significantly greater armor thicknesses compared to penetrators made of steel, alloys based on depleted uranium and ductile alloys of tungsten with iron or copper. This quality of the hard-alloy penetrators is due to the minimum deformation of the carbide core while passing through the armor, even with some damage to their structural integrity.
Unlike the hard alloys, penetrators made of heavy tungsten alloys (HTA) lose mass and significantly change their geometry when passing through an armor, while a kind of influx is formed on the nose of the penetrator, which significantly increases the collision area.
Hard-alloy penetrator of the 122mm 3BM11 APDS keeps its geometry even after certain damage to its structural integrity, the diameter of the cavity almost doesn't exceed the penetrator’s caliber
Due to the washout of the core material and a larger collision area, and other things being equal, tungsten alloy penetrators have a significantly lower penetration ability when firing at the barrier at acute angles, however, when interacting with obstacles at larger angles, the opposite trend is observed. Because of the plastic deformation during penetration, HTA penetrators change their trajectory much less than hard-alloy penetrators, and this quality becomes useful at large angles of impact with the obstacle.
In addition, when passing through spaced and combined armors, plastic deformation of the projectile mainly prevails in tungsten alloy penetrators, while hard-alloy ones are subject to brittle fracture in such obstacles.
Hard-alloy APDS after armor penetration
Tungsten alloy APDS after armor penetration
It is also important to note the influence of the penetrative nose pad of the APDS shells on armor penetration. A massive nose pad made of tungsten alloys reduces the denormalization of the APDS shell in the front layers of an armor at large angles, and also helps to reduce axisymmetric forces when penetrating into an armor. But the use of a nose pad leads to an increased consumption of kinetic energy in the front layers of the armor, which is spent on its deformation.
The 76mm Shot SV Mk.1 with compact penetrative nose pad and the 100mm 3NM8 with massive nose pad
Due to all the factors described above, early hard-alloy APDS with a compact penetrative nose pad are able to overcome much greater thicknesses at small angles than later APDS with a massive nose pads. Some shells feature the ultimate for their time penetration values for vertical obstacles. For example, the 120mm Shot L1G has impressive penetration at normal, comparable to 120mm APFSDS of the mid-80s!
APDS penetration values for rounds of the 20pdr and 120mm L1 guns, from Army Operational Research Group, Memorandum No. E.13 "Tank Effectiveness, Conqueror, Conway, and Charioteer." June 1954
However, you shouldn’t flatter yourself by the high penetration values - you could hardly meet an enemy with a homogeneous armor of that thickness exposed at normal to you. In fact, penetration values of these rounds against sloped armor are rather moderate. To correctly model the penetration scenarios of the APDS rounds with small penetrative nose pads we have added a set of slope-effects to correctly recreate penetration of armor at various angles.
A list of War Thunder hard-alloy APDS with compact nose pad:
37mm slpprj m/49
75mm slpprj m/49
76mm Shot SV Mk.1
84mm Shot Mk.3
100mm Type 1959 APDS
120mm Shot L1G