Clone trooper heavy gunners were one of the Grand Army of the Republic's heavy weapon specialist units.
These clone troopers were armed with some of the most powerful explosives and weapons in the army's arsenal, including missiles, grenades, demolition charges, and other heavy weaponry like cannons. Their main weapons were the largest ever designed to be used by clone troopers.
They sported some missiles on their belts as well as some targeting range goggles on their forehead and equipped with an communication device including some thick shoulder/sharp knee guards. They had three pouches on the front of their belt
Many heavy gunners were present at the Battle of Utapau when Order 66 was given. Three such troopers were assigned to eliminate Obi-Wan Kenobi, but they were instead killed by that Jedi Master. Soon thereafter, during the Raid on the Jedi Temple on Coruscant, heavy gunners were deployed into the Jedi Temple to bring down the ancient statues and pillars that supported the vaulted ceilings. These clones would later on serve in the Galactic Empire and become the heavily armed Imperial shock troopers.