Hyperion repeater pistols are very accurate but they have the feature of "reverse recoil": the longer the accuracy increases the longer the trigger is held. The listed accuracy on the weapon is what is achievable after the sustained fire increases their accuracy to maximum.
The Apparatus can come with a variety of barrels, each one can give the gun different properties:
Tediore barrel (standard) – Does nothing additional.
Maliwan barrel (elemental) – Increases elemental effect damage (if the weapon spawn with an element) and accuracy.
Dahl barrel (stable) – Increases recoil recovery and slightly reduces recoil and damage.
Bandit/scav barrel ("heavy") – Increases the weapon damage but reduces accuracy.
The variants of this pistol in Borderlands: The Pre-Sequel can spawn with Hyperion's new-style or old-style sets of materials and prefixes.
Old-style Apparatuses have higher damage output at the cost of significantly lower accuracy and fire rate. They also have a limited version of Hyperion's "reverse recoil" when aimed down the sights only.
The Apparatus is obtained randomly from any suitable loot source.