An Ion Rifle is an experimental Tau Ion Weapon designed for infantry use developed during the Tau Empire's Third Sphere Expansion. An Ion Rifle is similar in size to a Tau Rail Rifle, and it is a powerful weapon capable of engaging enemies at long ranges with high energy ion streams, vaporising flesh and metal with equal ease. These high-energy particles are accelerated by an electromagnetic field and react explosively with the target as a result of direct transfer of energy at an atomic level.
The Ion Rifle was developed using Ion Weapon technology acquired as part of a fruitful alliance between the Syrr'Tok Brotherhood of the Demiurg and the Water Caste of the Dal'yth Sept. However, despite the eventual widespread dissemination of Ion Weapons during the Tau Empire's Second Sphere Expansion, man-portable Ion Weapons remained an impossibility due to the bulkiness of their power sources. It was only the discovery of a Mor'tonium power source during the Third Sphere Expansion which made efficient powering of smaller-scale Tau Ion Weapons possible.
Tau Ion Weapon designs also allow for the weapons to be overcharged by exposing the reactive Mor'tonium power source to the environment, though this also exposes the user to the dangerous ionising radiation emitted by the Mor'tonium, and to the risks of overloading the primary power cells to hazardous energy levels. Overcharging an Ion Rifle allows it to generate an explosive blast with increased power compared to its normal fire mode.
Ion Rifles are currently only issued to Pathfinders as special weapons, where their firepower boosts the team's combat capabilities by allowing them to vaporise heavy infantry and light vehicles alike. Tau Interceptor Drones are also armed with a set of twin-linked Ion Rifles as standard weapons, which they use in conjunction with their advanced targeting systems to blow incoming aircraft out of the sky.
- Codex: Tau Empire (6th Edition), pp. 38, 48, 66-67
- Battlefleet Gothic Magazine 19, pg. 9
- Rogue Trader: Tau Character Guide (RPG), pg. 28