The operating handle is pulled to the opening position, this pushed the block to the side (to the right in the case of the PaK 40) and then a shell is pushed into the breach. The above pictures are of a horizontal sliding semi-automatic breech block. If the need arose, it could be used in an indirect fire role. Because of the weight and size, the gun was seen as a motorized piece and was equipped with solid rubber tires which allowed it to take the harsh punishment of the frontlines. The gun mechanism was of the ‘horizontal sliding breech block semi-automatic variety’” which allowed for a more rapid rate of fire, as the previous shell was expanded and the breach was left open for the next shot. The gun was equipped with a L/46 barrel with a larger double-baffled muzzle brake. For ease of production and economic use of resources, the curved gun shield of the Pak 38 was dropped and replaced with a more angular twin plate shield. As a result, a new carriage was developed using all steel construction.The gun’s traditional split trail was supported by torsion springs and, like the Pak 38, a third wheel could be attached to the trail spades for easier manhandling. Originally, Rheinmetall wanted to just change the barrel of the previous Pak 38 but, because the Luftwaffe was given priority for lightweight alloys, the design also needed to be changed.

However, soon after the factories geared up for production, the German military became aware of newer tank designs by the Soviets (thanks in part to the Molotov-Ribbentrop pact) and therefore ordered an upgunning of the Pak 38. What they came up with was the 5cm Pak 38 with a L/60 barrel (a barrel 60 calibers in length), which met approval for production in 1939. Rheinmetall-Borsig AG was asked to improve upon their original design. Whilst the 3.7cm Pak 36 anti-tank gun had acquitted itself very well during the Spanish Civil War, it was thought that an upgraded version was needed in order to stay ahead of the gun-armor spiral. The Wehrmacht was always trying to stay ahead of the arms race that had developed in the 1930s. Anti-Tank Gun – Approximately 20,000 Built Backbone of the German Anti-Tank Corps

Modern day anti tank guns