We all know how awesome the A-10 and GAU-8 is in aviation history. It is a flying gun. Well apparently it is not the first plane built around a gun. The Germans made something similar back in 1942. Henschel built the HS129.
According to worldwarwings.com:
Made by a company called Henschel, this ground attack aircraft was introduced in 1942 with the same idea A-10 engineers had in mind. They wanted to protect the pilots when performing low-level attacks. For this reason, they had a “bathtub” design which pushed the pilot as far toward the front of the cockpit as possible to increase visibility but also made it out of steel and very angular to deflect bullets. The canopy itself was made out of 3-inch armored glass.
Although it was also equipped with 2 machine guns, one of the later variant’s main weapon was the 75mm Pak 40 anti-tank cannon. As you can tell by the diagram, the whole feeding mechanism sat behind the cockpit with the barrel sticking out well ahead of it. At over 3,000 lbs, it was the heaviest gun installed in an aircraft until the A-10 Thunderbolt II was built around the GAU-8
Here is live footage of the HS129 firing its massive gun.
The 75mm projectiles look like missiles as they fly through the air.