History:

In 1944, Hitler wanted a self-propelled artillery vehicle equipped with a 23 cm RW62 rocket-powered mortar, with a maximum speed of 35-40 km/h, mounted on a Panzer IV tank chassis. This led to the concept of the Grille 23 SPG.

Despite having armor between 10-30 mm, this SPG had a maximum speed of 40 km/h and a large ammunition stock of 32 rounds (I only put 10 ammo to make it less laggy). Its characteristics were similar to the Nashorn or Hummel but with different tracks, transmission, and engine.

The reloading mechanism of the 23 cm RW62 mortar remains unclear—some sources suggest it would have used a crane similar to the Sturmtiger, while others believe it relied on manual labor.

The crew could have consisted of 5-6 members: Commander, Gunner/Loader, two Loaders, Radio Operator/Loader, and Driver. To accommodate 32 rounds of ammunition, the Panzer IV chassis was extended from its original 5.92 meters to 6.2 meters. However, in the end, this project remained only a paper concept, as Germany at the time prioritized the development of the Grille 17/21 SPG instead.