At first glance, the new Pak 40 was practically the same as the 50mm Pak 38 anti-tank gun, but the main difference was that Pak 40‘s gun shield was composed by flat steel plates rather than curved plates to facilitate production. Other changes not visible to the naked eye were that steel was used instead of light alloys, which significantly increased its weight. At this time, light alloys were being used in the production of aircrafts. The Pak 40 ended up weighing 1,425 kg, which eventually led to the need for more gun servers and motorized transport.The first 7.5cm Pak 40 gun was delivered for testing in November 1940, but it would not reach front-line units until 1942. Production started in 1942 and continued until 1945 and in these 3 years 23,303 towed guns were manufactured and around 3,500 that were installed in different models of tank destroyers. They were manufactured mainly in the factories of Ardeltwerke in Eberswalde, Gustloffwerke in Weimar and Ostlandwerke in Königsberg. This anti-tank became ubiquitous in all theaters of operations due to its excellent qualities and was able to hold off almost any Allied tank until the end of the war. It can be said that it became the standard anti-tank gun of the Wehrmacht.The Pak 40 anti-tank gun was a very well balanced weapon, with a 46 caliber long rifling barrel fitted with a muzzle brake and a semi-automatic horizontal sliding-block. The recoil system was of the hydropneumatic type and the life of the barrel was about 6,000 shots. It was normally operated by 6 servants who could fire up to 14 rounds per minute. The crew was composed by a gun chief, a prompter, a gunner, a loader and two suppliers. The barrel could rise between -5º and + 22º, and had a traverse of 65º (32.5º at each side). Each gun cost 12,000 Reichmarks and took about 2,200 man-hours to manufacture.The good performance of the Pak 40 led to different variants, being derived to be used not only as an anti-tank gun. Two variants were produced to be installed in vehicles, the 7.5cm KwK for tanks and the StuK 40 for tank destroyers. It was also used as a light field gun under the designations “7.5cm FK 40“, “7M59” and “7M85” and even as a coastal defense gun under designation “7.5cm Pak 40M in Lafette Marine 39/43“. However, the most striking variant was the one made to be installed on the Junkers Ju 88P-1 and the Henschel Hs 129B-3 ground attack aircraft, designated as “Bordkanone BK 7.5“.The Pak 40 used a wide range of ammunition, including the HE “SprG.34” round, the “Panzergranate 38 HL/B” which was a high-explosive anti-tank (HEAT) projectile with a shaped charge, the “Panzergranate 39” which was an armour-piercing, capped, ballistic cap (APCBC) projectile with explosive filler and tracer and the “Panzergranate 40” which was an armour-piercing, composite rigid (APCR) projectile with a sub-caliber tungsten core. In 1945, the Pak 40 became practically a dual purpose gun, since it was used as a field gun by many artillery units despite the fact that it could only rise 22º, which limited its range to only 8 km. In 1944, emerged a new variant with an improved angle of elevation of 35º, it was known as 7M59 and had a range of more than 13 km.The only Allied tanks capable of withstanding Pak 40 fire were the later British Churchill models, the Soviet IS heavy tanks and the American M-4A3E2 Sherman ‘Jumbo’and M26 Pershing tanks. In tests carried out against armour plate placed with an inclination of 30º the PzGr. 38 HL/B could penetrate 75mm from any distance, the PzGr. 39 penetrated 80mm from 1km and the PzGr. 40 penetrated 97mm at 1 km distance. Many Pak 40s were left intact, due to the difficulty of being moved if a position had to be quickly abandoned, or if the towing vehicle was damaged. Its enormous weight made it almost impossible for its servants to move more than a few meters in rough terrain or mud.The Pak 40 was distributed among some of Germany’s allies and some were captured. Many of these guns were kept in service until the 60s and 70s. Spain received 150 units in 1943, (within the Bär program), which were distributed in Anti-tank Guns Companies within the Infantry Regiments and in Tank Destroyer Battalions within the Divisions under the designation “CCC de 75/46“. Each antitank company had 6 guns distributed in three sections, and the Battalions had 18 guns. The Pak 40s shipped to Spain had 4 different models of wheels, so it is likely that they were used or from different production batches.In Spain, different trucks were used for transport, such as the ZIS-5, Chevrolet, Ford-K or the Dodge M-37 of 3/4 ton. The Spanish Army manufactured a specific ammunition for these guns, it was a subcalibrated projectile with a hard core made of widia (tungtene carbide) with a false dural warhead and cap (HVAPDS-C). These rounds had a muzzle velocity of 1,025 m/s and could penetrate 136mm of steel at 1,500 meters. These guns were in service until January 1977, with some units remaining as ornamentation in barracks and military installations, as well as in several museums.
