When the Empire learned of Kamino's plans for insurrection, the Sith Lord Darth Vader dispatched a special detachment of the 501st Legion, under the command of the bounty hunter Boba Fett, to Kamino with orders to annihilate the entire army of rebel clones. Thus, the Rail-class ARC troopers made their first and last stand alongside the Anti-troopers at the Kamino uprising in the year 12 BBY.
Following the rise of the Sith Lord Darth Sidious as Emperor of the galaxy, he quickly consolidated his Galactic Empire with an iron fist. Paving the way for Imperial rule were the Imperial stormtroopers, clones of the late bounty hunter Jango Fett that served as the Galactic Republic's clone troopers prior to the Emperor's ascendancy to absolute power. It was then that the Kaminoans found their homeworld placed under Imperial occupation by their own creations, no less.
Having made the mistake of indoctrinating the original Fett clones with absolute loyalty to the Republic, and thus the Empire, the Kaminoans sought to rectify their error by discreetly breeding a new clone army that was completely obedient to their Kaminoan creators. While the majority of the army was composed of Anti-troopers, a special force of elite soldiers were created to compliment the regular soldiers. Hence, the Kaminoans engineered a new generation of Advanced Recon Commandos—the Rail-class ARC troopers. Under the observation of the Kaminoans, the Rail-class ARCs and the rest of the rebel clones were grown and trained for nearly a decade.
The Rail-class ARC troopers were equipped with the ARC-variant Phase I armor, which included the command pauldrons and kamas. Their primary weapon was the chainguns.
Approximately twenty years after the Kaminoans created the first clone army for the Republic, the Sith Lord Darth Vader sent the 501st Legion to destroy the rebel clones and bring Kamino back into line. The 501st's mission commander was the bounty hunter Boba Fett, who also happened to be a clone of Jango Fett. While the Anti-troopers defended Tipoca City's outer perimeter, the Rail-class ARC troopers remained within the cloning facility to protect the batches of undeveloped rebel clones.
A Rail-class ARC trooper attacks Imperial stormtroopers during the Kamino uprising.
Despite their fast growth and training, the Anti-troopers proved to be no match against Fett and the battle-hardened stormtroopers of the 501st Legion, many of whom were veterans of the Clone Wars. After storming the facility, Fett and his stormtroopers were suddenly engaged by the Rail-class ARC troopers, some of whom tried to take the fight outside and prevent the Imperials from breaching the Tipoca City. Their efforts failed, however, and the life support systems were destroyed, thus aborting the unborn Anti-troopers before they had a chance to fight. With the rebel Kaminoans' capabilities to defend the city or grow another clone army severely diminished, they opted to escape from Kamino before the battle was completely lost.
In the meantime, the last of the Rail-class ARC troopers joined the remaining Anti-troopers as they desperately fought against their relentless Imperial clone brethren. Though they battled hard, Fett and the 501st stormtroopers succeeded in crowding the rebel clones out onto the platforms where they were exterminated to the last clone. With the death of the Kaminoan insurgents that bred the rebel clone army, the Rail-class ARC troopers perished along with the Anti-troopers and the "clone rebellion" not only ended in failure, but would never be publicly known since all information regarding the Kamino Uprising became highly classified.
Rail-class ARC troopers could be identified if a player targeted one of the chain-gun wielding troopers on Star Wars: Battlefront II during the level "Kamino: Changing of the Guard", an 'unofficial' clone revolution.