German Railgun - Zarco Macross

An 800 mm Schwerer Gustav shell at the Imperial War Museum…

Schwerer Gustav, Wiki

Dark Roasted Blend: The Biggest Guns in Human History

Schwerer Gustav or Dora the German 80 cm railway gun

Now that's what I call a gun! AnandTech Forums: Technology, Hardware, Software, and Deals

Weapons Of Great Wars - Schwerer Gustav was the name of a German 80 cm railway gun. It was the largest-calibre rifled weapon ever used in combat, the heaviest mobile artillery piece

Example of a round used in the Schwerer Gustav : r/pics

This is original ammunition railway wagons for Schwerer Gustav, displayed in czech republic : r/ww2

Big Shots – History's Largest Cannons, Mortars and Super Guns

What is the heaviest shell that can be fired from an artillery piece (not including ballistic missiles or rockets)? - Quora