Thursday, September 17, 2015

Panzer III Colours 4

ART BY Carlos de Diego Vaquerizo

39- Pz. Kpfw. III Ausf. L (Sd. Kfz. 141/1), 60. Inf. Div.
(mot.), Southern Stalingrad, U. S. S. R., October 1942. During the spring of 1942, the 60 Infanteriedivision (mot.) (60th Motorized Infantry Division) received other that a few backup subunits, a Panzerabteilung from the 18. Pz. Div. The illustration shows a camouflaged armored vehicle with colors Braun RAL 8020, Grau RAL 7027 and Grün RAL 6007, having on its fenders the emblem of the 60. Inf. Div. (mot.), two small yellow crosses one on top of each other. This was one of the units that was annihilated in the Stalingrad siege. During the spring of 1943 several Infanteriedivisionen (mot.) were reformed, at least in theory, with a Panzerabteilung (armored vehicle battalion) a Panzerjägerabteilung (armored vehicle hunters) and an Aufklärungsabteilung (reconnaissance battalion), and from that moment on were renamed Panzergrenadierdivisionen; around this date a new formation was created; the 60. Pz. Gren. Div. a, which was finally called the Pz. Gren. Div. "Feldherrnhalle".

40- Pz. Kpfw. III Ausf. J (Sd. Kfz. 141), SS-Pz. Gren. Div. "Wiking", Caucasian region U. S. S. R., November 1942. Between September 1942 and November of that year, the Waffen SS "LSSAH", the "Das Reich", "Totenkopf" and "Wiking" divisions were upgraded to panzergrenadierdivisionen. As it has been mentioned, much war material that was intended for Northern Africa ended up on the Eastern Front, so in 1942 many vehicles with a tropical camouflage were seen on the Caucasian region. This Panzer III has been camouflaged before it got out of the factory with the official camouflage pattern approved in March, which is basically a Braun RAL 8020 base with Grau RAL 7027 spots occupying approximately 1/3 of the armored surface. The Swastika that identified the "Wiking", a "Sonnenrad" (a sun shaped rune), can be seen in the frontal right sided fender and in the rear left fender. On top of the spares wooden box on the turret there is a painted Swastika for aerial ID purposes.

Panzer III Colours 3

ART BY Carlos de Diego Vaquerizo

35- Pz. Kpfw. III Ausf. H (Sd. Kfz. 141), Pz. Rgt. 8, 15 Pz. Div., El Alamein, Egypt, October 1942. At first sight, the armored vehicles of the 15. Pz. Div. could be told apart from those of the 21. Pz. Div. by the numeral system: The first ones had a single big digit on both sides and on the back of the turret, while the second ones had three digit numerals. The "lonely" numeral in this case is a "6" the numeral identifies the company so this Panzer III belongs to the 2. Kp. of the II. Abt. The formation numerals can be seen in full on both sides of the frame in a smaller size. On the rear of the turret, on top of the division insignia, we can see the emblem of the Pz. Rgt. 8, a "Z" shaped rune reversed and lying down. This motif was called "Wolfsangel". Some armored vehicles in this unit had the top of the rear wooden box behind the turret painted red in order to be properly identified by fellow German aviators.

36- Pz. Kpfw. III Ausf. N (Sd. Kfz. 141/2), sch. Pz. Abt. 501, Kairouan, Tunisia, January 1943. In the Stab of this schwerepanzerabteilung we could find the Tiger "01" and "02" and a leichte Zug (light squad) with eight Panzer III's armed with a 75mm gun and numbered "03 to "10". The Panzer III arrived to Northern Tunisia painted with Braun RAL 8020 paint, a color tone which was not appropriate for this region with lots of green vegetation, so most vehicles were covered up with green paint, although in some cases only large green spots were painted. It makes sense to assume that we're dealing with Grün RAL 6007, but Feldgrau RAL 6006 and even Olive Drab paint
(captured from US forces) could have been used. The insignia for this unit; a lurking tiger, can be seen in the front right by the drivers' sight

37- Pz. Kpfw. III Ausf. M (Sd. Kfz. 141/1), 4./SSPz. Rgt. 3, SS-Pz. Gren. Div. "Totenkopf", Jarkov, U. S. S. R., March 1943. The Heer armored vehicles' divisionary emblems were usually painted yellow, but the Waffen SS vehicles were painted white. This Panzer III with white Weiss RAL 9001 camouflage paint, has its division emblem (a skull) right by the drivers' sight. The 4. Kp. from the SS-Pz. Rgt. 3 was a schwere Panzerkompanie (heavy armored vehicle company), and was equipped from the start with nine Tigers and ten Panzer III, but in May 1943 it was reduced to six Tiger and was reorganized as the 9. Kp.

38- Pz. Kpfw. III Ausf. M (Sd. Kfz. 141/1), 8./SS-Pz. Rgt. 2, SS-Pz. Gren. Div. "Das Reich", Jarkov, U. S. S. R. March 1943. The 8. Kp. from the SS-Pz. Rgt. 2 was a schwere Panzerkompanie which as it was customary and due to the slow manufacturing process of Tiger armored vehicles, had at first ten of these and twelve Panzer IIIs. The commander of this vehicle died in combat in March the 14th 1943 while conquering back Jarkov. Towards the end of that month, the company had some days off to get some provisions and recover from battle, and crews wrote the name of their fallen companion on both sides of the turret. The division emblem a "Wolfsangel", can be seen right by the drivers' sight and on the rear plank of the vehicle's frame. On top of the factory painted Gelbbraun coat, thin irregular lines of Dunkelgrau have been painted.

41- Pz. Kpfw III (FI) Ausf. M (Sd. Kfz. 141/3), Pz. Rgt. 11, 6. Pz. Div., Kursk, Southern Sector, U. S. S. R., July 1943. For the offensive that took place in the Kursk peninsula and with the purpose of confusing the Russian secret services, the Germans changed their insignias on every division that was to be a part of this offensive. The new insignias were simple geometric figures. The new one for the 6. Pz. Div. was a reversed double "T" with uneven arms; it was usually painted on all four sides of the vehicle and was simultaneously used along with a small four armed star, although this star was only painted on the front and back of the vehicles' frame. The system for identifying the different units of this division was to paint the abbreviated form of the commander's family name. For example the commander of the Pz. Rgt. 11 (only the second battalion was available here) was Von Oppeln- Bronikowski, his armored vehicles were painted with the letters "Op". The Flammpanzer (armored vehicle with flame thrower device) portrayed in this color profile has been camouflaged with the color pattern of 1943: Dunkelgelb RAL 7028, Olivgrün RAL 6003 and Rotbraun RAL 8017.

42- Pz. Kpfw. III Ausf. M (Sd. Kfz. 141/1), SS-Pz. Rgt. 3, SS-Pz. Gren. Div. "Totenkopf", Kursk, Southern Sector, U. S. S. R., July 1943. The temporary insignia for this division of the Waffen SS in the "Zitadelle" operation was a "Dreizackrune" or trident shaped rune: Three vertical bars painted in either white or black paint on the front and back of the vehicles. In spite of having three authorized battalions, the SS-Pz. Rgt. 3 only had two, with three companies each. This armored vehicle has numerals "II5" on both sides and the back of the turrets' shielding, indicating that this vehicle belongs to the Stab of the II. Abt. Camouflage consists of a series of irregular Olivgrün paint gun strokes on top of the factory painted Dunkelgelb.

Panzer II Colours 2

ART BY Carlos de Diego Vaquerizo

31- Pz. Kpfw. III Ausf. F (Sd. Kfz. 1941), Pz. Rgt. 2, 1. Pz. Div., France, June 1940. In 1940 this division took the oak leaf as their distinctive, a motif that was usually drawn in the front and rear of the armored vehicles' turret. The armored vehicles of the Pz. Rgt. 2 could be told apart from those of the Pz. Rgt 1 thanks to a painted dot after the formation numerals. Some units had a white cross for aerial ID purposes on top of the turret, a marking that was sometimes accompanied by a rectangle in the same color painted on top of the motors' cover.

32- Pz. Kpfw. III Ausf. E (Sd. Kfz. 141), Pz. Rgt.
31, 5. Pz. Div., Balkans, May 1941. The emblem that the OKH gave to this division in 1941 was an "X" which the armored vehicles had painted in the front, on both sides and on the back of the frame. The Pz. Rgt. 31 had a particular insignia named "Rot Teufel" (Red Devil) painted on both sides of the turret. This armored vehicle has its tactical numerals painted only on both sides of the frame; on the back of it we see a stencil with five small digits; these are the vehicles' frame number, in red.

33- Pz. Kpfw. III Ausf. G (Sd. Kfz. 141), Pz. Rgt. 5, 21. Pz. Div., Sidi Rezegh, Libya, November 1941. Under the brief and worn Gelbbraun RAL 8000 coat, we can see the factory painted Dunkelgrau RAL 7021 of this Panzer III. On both sides of the turret and on the "Rommelkiste" (Rommel box) screwed to the back of it, we can see painted white the numerals that tell us that this is the third armored vehicle from the first section of the first company. The Afrikakorps palm tree can be seen on both sides of the frame, and on the back of it we can see this motif right by the division insignia. Both motifs are also painted on the frontal armored plank, between the drivers' sight and the machine gun, although partially concealed by some spare track links set there to "increase armoring".

34- Pz. Bef. Wg. III Ausf. E (Sd. Kfz. 267), Pz. Rgt. 5, 21 Pz. Div., Bir Hakeim Libya, May 1942. This Panzerbefehlswagen (commanding armored vehicle) repainted Gelbbraun does not have its division emblem, but it does have the DAK palm trees. These motifs have been painted with the same color used for camouflage, while the crosses and numerals are white with hollow (unpainted) inside. This type of vehicle was equipped with several pieces of radio equipment, and because the lack of room, its turret was fixed (not moveable) and the gun was a decoy as well; after having lost the fake weapon on a fight, crews have placed a piece of wood to accomplish the function of the previous one.

Panzer II Colours 1

 ART BY Carlos de Diego Vaquerizo

29- Pz. Kpfw. III Ausf. L (Sd. Kfz. 141/1), sch. Pz. Abt. 502, Tortolowo U. S. S. R., September 1942. Heavy armored Tiger vehicles were manufactured slowly, so in the schwere Panzerabteilungen, (Independent battalions of heavy armored vehicles) a few Panzer III's were included. At some point in this year, in the Stab of the 1. Kp. there were Tigers "100" and "101", while vehicle number "102" was a Panzer III that was replaced in October of that year for a Tiger. The color of this vehicle once it got out of the factory seems to be one of the light grays employed by the Luftwaffe, but it could also be Grau RAL 7027; the unit that the vehicle was entrusted to, painted some Feldgrau RAL 6006 camouflage spots. The battalion insignia, a mammoth drawn in a white outline, can be seen right by the machine gun in the front and on the back of the turret. The style in which the Balkenkreuz is painted is quite interesting because of the unusual color array.

30- Pz. Kpfw. III Ausf. J (Sd. Kfz. 141/1), Pz. Rgt. 15, 11. Pz. Div., southern sector of the Eastern Front, U. S. S. R., July 1942. The official distinctive of this division was a circle divided by a vertical bar, which was usually painted on all four sides of the armored vehicles. This unit also employed another symbol; a ghost yielding a sword and reclined on the front of a vehicle in motion. The motif was painted on both sides of the frame and in the large box that most armored vehicles had in the back. The Pz. Rgt. 15 was known for painting on its vehicles formation numerals with only two digits: the first one indicated the squad and the second one the position of the armored vehicle inside the squad. On top of the Grau RAL 7003 base coat, elongated Grün RAL 6007 spots have been painted to camouflage the vehicle.

Tuesday, August 11, 2015

Cutaway - Pz.III

ART BY Carlos de Diego Vaquerizo

The Panzer III crew consisted of five men with two in the front of the hull including a driver at the left and a radio operator/hull machine gunner at the right. Up in the turret, the gunner sat to the left of the main weapon in typical German style, a loader worked the gun on the right side, and the commander sat elevated at the rear with the use of a cupola over his head for battlefield observation. Both the gunner and commander sat in padded seats suspended from the turret ring, rotating with the gun. But the loader had the use of a small fold down seat attached to the back firewall and typically worked standing up on the hull floor with his seat stowed. Most of these Ausf. E and F panzers were manufactured between 1938 and 1940 by Daimler-Benz, Maschinenfabrik-Augsburg-Nuernberg (MAN), and Henschel & Sohn, and together these firms produced 96 Ausf. E and 435 Ausf. F vehicles. The basic interior layout of the Pz. III would remain unchanged throughout the remainder of the production run but most of the major components would continue to improve, particularly up in the turret, as experience was gained in combat.

Unlike the early 3.7cm gun, the 5cm weapon and coax were protected behind an external mantlet. But in these models there were two viewing flaps in the mantlet, one on each end, and both of them are visible here. The additional right flap allowed the loader the same unrestricted view out the front of the tank as the gunner had. Notice the lead weight attached to the rear of the recoil guard to help balance the barrel heavy weapon.

The 5cm gun fired three ammo types. The high explosive (HE) was known as Sprenggranate 38 (Sprgr. 38), which was nose fused for impact detonation. The second type was an armor piercing capped shell of the typical German penetrating and bursting type called Panzergranate 39 (Pzgr. 39). The piercing cap on the end of the projectile helped reduce shattering upon contact with the target. The third type was Panzergranate 40 (Pzgr. 40) and this was a light weight projectile with a very heavy tungsten carbide core. Sometimes known as armor piercing composite rigid (APCR), this projectile reached a very high muzzle velocity at close ranges due to its light weight, but its velocity decreased rapidly at distance for the same reason. Because tungsten was at a premium in Germany, this shell was never offered to tankers in abundant quantity, but when battling at close quarters the Pzgr. 40 was a powerful armor piercing shot.

The Pzgr. 39 was one of a number of German bursting AP shells (called "Supercharged" by the Allies) which were particularly effective against Allied tanks where ammo was often stored unprotected inside the hull or turret. This was because the Pzgr. bursting charge detonated just after penetration, causing extensive internal fires and ammunition explosions with subsequent serious injury or death to the crew. On the other hand, Panzer III ammo rounds were stored in armored cabinets (4 to 6mm thick) below the turret ring, and Allied AP rounds that managed to penetrate the external armor skin were less likely to set them off. This was because the damage caused by most allied solid AP shells was restricted to the kinetic energy left in the round after penetration.

The next major changes in the evolution of the Pz. III centered on yet another increase in armor thickness to 30mm, requiring a new driver's visor 30 and an improved KFF2 periscope in the new Ausf. G tanks. With an improvement in the turret wall design to provide more room inside, an improved cupola was also added, the same cupola that was also mounted on later Pz. IV tanks. As with the mid production cupola mentioned earlier, the late style cupola required only one lever to open and close the upper and lower shutters that protected each of the cupola's five viewing blocks. But now the shutters were smaller, only the width of the view opening, and the operating lever inside was made to fit into détentes that fixed the shutters fully opened, half opened, and fully closed. Although the first batches of these new Ausf. G and J tanks were originally built with the 3.7cm guns, all later vehicles of these types were fitted with the KwK38 L/42 5cm weapons. By the end of 1942, most of the earlier Panzer III tanks that were still in service had been updated with the 5.0cm gun and very few photos show vehicles with the smaller caliber weapon from then on.

The short barreled 5.0cm L/42 was not powerful enough to penetrate many of the Soviet tanks they encountered during their Blitz into Russia and the longer KwK39 L/60 gun was substituted for the shorter weapon at the factories during the Ausf. J production run. Although the gun breech of both the L/42 and L/60 guns is identical from inside the vehicle, the longer ammo rounds of the later gun required some rearranging of storage in the hull and a reduction of numbers. Those vehicles with hull side escape hatches could store around 84 of these longer rounds while later Ausfs., with the hatches deleted, had room for 98.

Friday, July 17, 2015

Sturmhaubitze 42, Sd.Kfz 142/2 Late-Production

In October of 1942 Sturmhaubitze 42 was produced by Alkett, its design was based on Stug III Ausf F and F/8's chassis and it was armed with 105mm StuH 42 L/28 (L/30) howitzer. From 1943 onwards StuH 42 was built on Ausf G's chassis. Vehicles of this type were modified in the same way as Ausf Gs were. Early vehicles were fitted with muzzle brakes but since September of 1944, it was decided that it wasn't needed.

In August of 1940, Sturmartillerie units were reorganized into Abteilungen (battalions) with 18 assault guns in three batteries (with 6 assault guns each). In early 1941, the battalions were renamed - Sturmgeschuetz Abteilungen and batteries to Sturmgeschuetz Batteries. In March/April of 1941, all Sturmgeschuetz Batteries had the number of assault guns increased to seven. In 1942, with the introduction of long-barrelled Stug III (75mm L/43 and L/48), Sturmgeschuetz Abteilungen were reformed and number of assault guns was increased to 28 per battalion. Each battalion still had three batteries but number of assault guns in platoons was increased to three. In November of 1942, Sturmgeschuetz Abteilungen were reformed again and number of assault guns was increased to 31 per battalion with three additional assault guns for battery commanders. This type of organization often referred to as Sturmgeschuetz Brigade remained in use until the end of the war. In June of 1944, new organization scheme was introduced - Sturmartillerie Brigade with 45 assault guns, including 33 Stug III/IV (75mm L/48) assault guns and 12 Sturmhaubitze 42 (105mm L/28) assault howitzers. Brigade had three batteries with 2 Stug IIIs for each battery command, while each battery had two platoons of four Stug IIIs and one of four StuH 42s. This organization scheme was used alongside the Sturmgeschuetz Brigade scheme to the end of the war. In practice, these ideals were hardly ever achieved and then only highly favoured formations received the full complement.

Sturmhaubitze 42, Sd.Kfz 142/2 Mid-Production

In 1942, a variant of the StuG III Ausf.F was designed with a 105 mm (4.1 in) howitzer instead of the 7.5 cm StuK 40 L/43 cannon. These new vehicles, designated StuH 42 (Sturmhaubitze 42, Sd.Kfz 142/2), were designed to provide infantry support with the increased number of StuG III Ausf F/8 and Ausf Gs being used in the anti-tank role.

The StuH 42 mounted a variant of the 10.5 cm leFH 18 howitzer, modified to be electrically fired and fitted with a muzzle brake. Later models were built from StuG III Ausf. G chassis as well as StuG III Ausf. F and Ausf. F/8 chassis. The muzzle brake was often omitted due to the scarcity of resources later in the war. 1,211 StuH 42 were produced from October 1942 to 1945.

The early models got the old boxy gun mantlet armor without a machinegun and the machinegun behind the classic shield which had to be operated from the outside. Late models were fitted with the Topfblende (pot mantlet) (often called Saukopf (Pig's head)) gun mantlet without coaxial mount. This cast mantlet with organic shape was more effective at deflecting shots than the original boxy mantlet armor of varying thickness between 45 mm and 50 mm. Lack of large castings meant that boxy mantlet was also produced until the very end.

Coaxial machine gun was added first to boxy mantlets and then to cast Topfblende, in the middle of "Topfblende" mantlet production. With an addition of coaxial, all StuGs carried two MG 42 machine guns from fall of 1944. Later, the Topfblende mantels are be produced without machine gun opening so there are two verions of the late models. The machine gun on the roof, could now be operated via inside. Also a smaller armor plate was provided for the protection of the weapon.

Sturmhaubitze 42, Sd.Kfz 142/2 Initial Production

In 1942, a variant of the StuG III Ausf. F was designed with a 105 mm (4.1 in) howitzer instead of the 7.5 cm StuK 40 L/43 cannon. These new vehicles, designated StuH 42 (Sturmhaubitze 42, Sd.Kfz 142/2), were designed to provide infantry support with the increased number of StuG III Ausf. F/8 and Ausf. Gs being used in the anti-tank role. The StuH 42 mounted a variant of the 10.5 cm leFH 18 howitzer, modified to be electrically fired and fitted with a muzzle brake. Production models were built on StuG III Ausf. G chassis. The muzzle brake was often omitted due to the scarcity of resources later in the war. ~1,299 StuH 42 were produced by Alkett from March 1943 to 1945, the initial 12 vehicles were built on repaired StuG III Ausf. F and F/8 from autumn 1942 to January 1943.

Thursday, April 16, 2015

How effective were AT rifles against the Pamzer III?

The case of the Pz IIIs. 

All the Pz IIIs with 37mm guns had only 30mm of front armor. The first 50L42 armed model, the G, had the same. The first to uparmor, to 30mm plus 30mm additional bolted on the front hull only, was the H model. The turret was still 30mm, at around 15 degrees slope (the G and H mantlets were somewhat thicker, 37mm). Both Gs and Hs were made between the fall of France and the invasion of Russia, with twice as many of the G model produced as Hs. 

By the time of the invasion, production of the J model with the 50L60 gun had begun, but most of the existing fleet were the older models. This model had 50mm front plates factory built, and a 50mm mantlet, but the rest of the turret front was still 30mm. The J series had the largest production run of any of the letters, as production began to ramp in 1942. They were produced from before the invasion until a year after it. 

The last year of Pz III production, as tanks rather than StuG that is, were the L-N versions, from mid 1942 to mid 1943. These had 57mm turret fronts, 50mm base front armor elsewhere, and in addition 20mm additional plates bolted on to the upper front hull and gun mantlet. Through this whole uparmoring process, the turret sides and rear, and the hull sides, remained 30mm only. 

The final production vehicle of the Pz III series was the StuG. The early StuG had the 75L24 gun, same as in the Pz IV, and had 50mm of front armor - like the Pz III J model - with the same 30mm sides naturally, since they used the same chassis as the Pz III tanks. By late war standards, not many of these were produced. 

The first upgunned StuGs, the F models, had 75L43 guns, and originally the same armor as before. The same expedient of bolting on extra armor plate was used, to thicken the front from 50mm to 50mm+30mm (going from 2 inches up to 3 inches thick, basically). The gun mantlet was not uparmored and remained 50mm. Late model F series, toward the end of 1942, had the 75L48 and the extra bolted armor. 

The last production model of the StuG III, the G model, was the type produced from 1943 to the end of the war, and in the late war by far the most common type. Everything you'd see in CMBO is this model. It had 80mm front armor factory built, and the 75L48 gun. The sides are still the same 30mm as the original Pz III had all around - plus skirts.

The side armour of the StuG and Panzer IV were just as weak in 1944 and 1945 as they were in 1943 when Schürzen was introduced. The AT-rifle also remained effective against lightly armoured vehicles like the SdKfz 251, effectively an infantry fighting vehicle operating against Soviet infantry.

According to Steven Zaloga, approximately 1/2 million AT-rifles were produced during the war with 37.000 still being turned out in 1944 and the Soviet Rifle division nominally had 111 such weapons in its inventory in June 1945 (down from 279 in 1942).

Of course, Schürzen were originally tested against direct HE fire as well, and that threat hadn't disappeared either.

KPB - AT Machine gun (1944) Penetration 32 MM at 90 degrees at 500 meters. ROF 70/minute. 
PTRD - (1941) AT rifle Penetration 37mm at 300 meters. 

PTRS (1941) AT rifle. ROF 15/minute, Penetration 35mm at 90 degrees at 300 meters, 25mm at 500 meters. Germans used captured ones as PzB 783(r). Could penetrate 50mm vertical armor at 100 meters. (PzIV had 50mm vertical front armour) 

So at very close distances these could be quite deadly to tanks like PzIII and PzIV.

The official design requirement was that at a range of 500m it should penetrate 20mm of case-hardened armour at 70 degrees.

The BS.41 bullet used in the ATRs had a tungsten-carbide core and was a very good performer. I have figures of penetration (at 60 degrees in all cases) of 30mm/100m, 27.5mm/300m and 25mm/500m.

The penetration data is for 60° from vertical, or 60° from horizontal (30° from vertical).

Penetration loss with range looks very small for such a light weight round.
60 degrees from horizontal.

The 14.5 fires a heavy bullet which probably doesn't slow down that much up to 500m, but I agree that the fall-off in penetration looks low. The figures are from a secondary source on anti-tank rifles. If anyone has a primary source I would be interested.

The 14.5mm API had a small-arms style of bullet, i.e. with a complete streamlined jacket (in steel, coated with gilding metal or (later) zinc) and with the AP core filling most of the bullet. There was a gap between the blunt-nose core and the jacket tip and this was filled with incendiary material. This design was copied by the US for their .50 cal M8 API round used in late-WW2 and Korea aircraft guns.

In the BS.41 the core was tungsten carbide and the bullet short and flat-based. In the BS-32 (which may have followed it into production) the core was steel and the bullet longer and boat-tailed.

My source is Labbett & Brown's Technical Ammunition Guide 2/4 on Soviet 12.7mm and 14.5mm ammo - very good, lots of sectioned drawings!

I suspect that the main advantage of the plates was that penetrating them might cause the bullet to tumble and hit the armour side-on, greatly reducing effectiveness.

The Luftwaffe found out that just penetrating 3mm alloy aircraft skin before hitting armour would reduce effectiveness of AP bullets by up to 30%.

Thoma - or Drahtgeflechtschürzen were adopted in September '44, starting with Fgst.Nr. 92301, so any unit receiving Pz IV Ausf. J after this date should theoretically have them, although the usual first in/last out process of assembling tanks may throw a spanner or two in the works here.

The small-caliber AT-rifles used early in the war (7.92mm etc.) was not very effective. The Soviet 14.5mm PTRD and PTRS were different beasts all together. They were effective against lightly armoured vehicles like the German SPWs (SdKfz 250/251) and sufficiently powerful to cause the Germans to adopt "Schürzen" to protect the lower hull of the Panzer III, IV and Sturmgeschütz.
The entire Panther project was nearly cancelled because the lower hull armour was considered to weak to withstand (future?) Soviet AT-rifles. Had it not been possible to put Schürzen on the Panther, it would have been replaced by the Panther II! (See Jentz: "Panther..." p. 35 and 53)

The German problem with the Soviet AT-rifles was not that they were very effective against German tanks - the problem was that on a good day with a lucky gunner, one of these dirt-cheap and primitive weapons could knock out a 100.000 Reichmark tank. That was not acceptable and the Germans put a lot of design effort into conquering this problem.

Of course, the AT-rifles would also be effective against vision slots, periscopes and other weak spots and openings in the tanks armour.
One would think that expanded metal grating would be not much harder to produce than plate, while providing the weight and material savings of wire mesh. Or was such a product not part of the German industrial "toolkit" in the 1940's?

Sound dumb does it not? Well, it is

It was not the wire-mesh shields that posed problems, it was the brackets attaching them to the hull. None had been developed at this time (February 1943) and designing them would delay the issue of Schürzen. (Jentz/Spielberger: "Begleitwagen.." p. 198)

When Schürzen were first tested in 1943, both wire-mesh and plate were used. Results showed that both were equally effective in stopping AT-rifle rounds and HE. It was decided to use plates because wire-mesh was more complicated to produce and the facilities for producing plates were already there (see Jentz & Spielberger: “Begleitwagen” and Spielberger: “Sturmgescütze...”)

Schurzen Side Skirts
The previously mentioned Schuzen side-skirts became a topic of discussion during the Fuhrer's conference on 6 and 7 February 1943. Hitler was quite in agreement with mounting skirts on the Panzer III, IV and Sturmgeschutz to provide protection against Russian anti-tank rifles. Test firings on Schurzen protective skirts (wire and steel plates) were reported on February 20, 1943. Firing tests utilizing the Russian 14.5mm anti-tank rifle at a distance of 100m (90 degrees) showed no tears or penetration of the 30mm side armor, when protected either by plates or wire mesh. When testing was conducted with the 75mm high explosive shell (Charge 2) from a field gun, there was no damage to the sides of the hull armor when protected by the wire or plates. Wire mesh and plates had indeed been penetrated and even torn away, but, they still remained usable.
The decision to utilize the plates as opposed to the wire mesh (although both had proven effective and the mesh was lighter) was based on the fact that the wire mesh required the design of a new mount, which would have required additional time to be developed.
Additionally, the procurement of wire mesh for the side skirts was difficult. The skirts were not tested against shaped charges, nor were they intended as protection against shaped charge (HEAT) shells.
On March 6 1943, Hitler indicated that he was satisfied with the favorable results of the firing tests against the Schurzen side skirts. In addition to outfitting all newly produced Sturmgeschutz, Panzer IV and Panthers with side skirts, all armored vehicles of these types currently deployed and those undergoing maintenance, were to be backfitted with them. The schedule for fitting Schurzen was to be expedited.