12 . 8 cm Pak 44 The 12 . 8 cm Pak 44 , ( Panzerabwehrkanone ) was a German heavy anti - tank gun used during World War II . It was designed as a result of experiences on the Eastern front in 1943 . The German army had encountered the Russian 122 mm guns and had issued a requirement for a similar weapon . Development initially concentrated on a field gun known as the Kanone K 44 . However once heavier Russian armour such as the IS - 2 started to appear the design requirements were altered to include an anti - armour role . The Pak 44 had short to medium - range performance similar to the 8 . 8 cm Pak 43 , but the 12 . 8 cm Pak 44 better maintained its anti - tank performance over long to extreme - long ranges ( 2000 – 3000 + yards ) while also doubling as an effective field gun when firing HE . Design history . The choice of 128 mm was made because of the availability of tooling due to the use of this caliber on naval weapons , design contracts being awarded to Rheinmetall Borsig and Krupp , the first prototype guns were delivered for testing in late 1944 . Rheinmetall began development on a variant of the 128 mm FlaK gun . whilst Krupp opted to design a new weapon from the ground up . After initial tests the Rheinmetall design was dropped and development continued with the Krupp design . However the service tests showed that a towed anti - tank gun weighing nearly 11 tonnes was impractical so the towed design was terminated . Approximately 50 barrels and breeches were used on existing carriages . The weapon that used the ex - French GPF - T carriage was known as the K 81 / 1 while the K 81 / 2 used the ex - Russian carriage . Both of these designs were rushed , and were too heavy , making them cumbersome to deploy . In 1943 the design was started for a gun to mount on the Jagdtiger ( Sd . Kfz . 186 ) and the Maus super - heavy tank was started using the Pak 44 as its starting point . This weapon of which approximately 100 were made was known both as the Pak 44 and Pak 80 / " Panzerjägerkanone " Pjk 80 . Performance was identical to the initial design . Performance . The gun was fed with two - piece ammunition , the projectile and cartridge making up separate pieces . Because of this the gun could be fired using three different sized propellant charges , a light , medium and heavy charge . The light and medium charges were normally used when the gun was fulfilling the role of an artillery piece , where they would launch the ~ 28 kg projectiles to a muzzle velocity of 845 m / s and 880 m / s respectively . Finally the heavy charge was used when the gun was fulfilling its intended role as an anti - tank gun , where it fired a 28 . 3 kg APCBC - HE projectile ( PzGr . 43 ) at a muzzle velocity of 935 m / s . With the heavy charge , and using the PzGr . 43 projectile , the Pak 44 was capable of penetrating just over of 30 degree sloped armor at 1000 meters , and at range . The 12 . 8 cm Pak 44 ended up becoming the standard main armament for the Jagdtiger heavy tank destroyer , as well as being the planned main armament for most of the future heavy tank designs in development during the dying months of World War II , including the Maus and E - 100 . Designations . As is common at this time this weapon underwent several name changes . At various times it was known as K 44 , Pak 44 , Kanone 81 , Pak 80 and Pjk 80 . The equipment numbered in the 8x range were temporary equipment issued usually in small numbers and not regarded as standard issue service weapons . Hence Pak 80 and Pjk 80 were temporary names as were K81 / x . Had this equipment been accepted into full service it would have had a Pak 4x designation attached . The only difference between the Pak 44 and the K 44 was mode of operation — the weapon itself was identical .