As the first weapon picked up by a character at the start of a playthrough, the React Repeater is a minimalist pistol with no special characteristics beyond its unique parts and should be replaced when better weapons become available.
The React Repeater spawns with an entirely fixed set of parts consisting of a Tediore grip and barrel, no sight, no accessory, and no elemental capacitor.
Weapons with the same name can spawn in the game but without any restrictions on parts, sights, or elemental capacitors.
The title of this weapon is in fact "Repeater"; "React" is treated as a prefix by the game engine. However, "React" can never be replaced with another prefix because all parts are fixed.