Requiring a new anti-armor solution to combat the rise in improved Soviet armor along the East Front during World War 2 (1939-1945), the German Army began looking into a long-range Anti-Tank (AT) gun to pair with its existing anti-armor stock. The introduction of the T-34 Medium Tank had already proven itself a nasty surprise to the Germans and the IS-2 (Josef Stalin) Heavy Tank only served to raise the bar in terms of combined firepower and armor protection. This initiative produced the late-war PaK 44 series Heavy Anti-Tank Gun.
Both Rheinmetall and Krupp were commissioned for prototypes but neither of these designs were directly adopted for service. Instead, 12.8cm Krupp barrels with their integral breech systems were mated to carriages that had been previously captured from French and Soviet Army stocks - becoming the 12.8cm PaK 44. The weapon became a useful, though limited, towed artillery weapon with a inherent field gun value to go along with its intended AT capabilities. A gun shield was affixed to the breech area to offer some level of protection for the gunner crew.
The PaK 44 fired a semi-fixed Armor-Piercing (AP) shell weighing 62 pounds for the AT role and, when used as a field gun, the gun made use of a 62 pound High-Explosive (HE) projectile. In either case, the shell's caliber measured 128mm and loading was through a semi-automatic horizontal sliding breech block arrangement. The recoil mechanism was of a hydropneumatic design. Both components sat upon either a split-trail wheeled carriage form or a cruciform0style wheeled carriage assembly based on supplies on hand. Elevation and traverse controls were appropriately included and allowed for an elevation span of -7 to +45 degrees with traversal being limited by the carriage in play - some were able to perform a full 360-degree swing. Muzzle velocity of the outgoing shells reached 3,100 feet per second and maximum range was out to 26,700 yards. Overall weight of the complete system tipped the scales at 22,400 pounds and the L/55 barrel reached a length of 20 feet.
In practice, the PaK 44 was an effective yet heavy battlefield instrument, cumbersome to transport and arrange for fire. Its AP shells were able to provide the necessary penetration values at range without reduction in performance over distance - a limiting factor of the preceding PaK 43 series guns (88mm). The late-war appearance ultimately limited manufacture of the PaK 44 guns to just 51 units. These entered service before the end of 1944 and fought on through to the end of the war in Europe in May of 1945.
The PaK 44 was also produced for the "Jagdtiger", a tough self-propelled tank destroyer appearing late in the war though with only 88 examples to its name. It was to also fit into the upcoming E-100 and Maus super-heavy tank designs that saw development by the Germans before the end of the war - though neither of these additions were finished products by any stretch. At least 100 guns were committed to these vehicle ventures, apart from the 51 used in the PaK 44 artillery role.