Hyperion repeater pistols are very accurate but they have the feature of "reverse recoil": the longer the firing of them, the higher the accuracy. The listed accuracy on the weapon is what is achievable after the sustained fire increases their accuracy to maximum.
Impacts use the Torgue barrel, giving them notably increased damage, at the costly price of decreased accuracy and increased recoil, as well as slower reload speed and fire rate.
The variants of Impacts in Borderlands: The Pre-Sequel commonly spawn with Hyperion's new-style materials and prefixes which are the same as in Borderlands 2.
In addition to the Impact, a variant of this weapon exists in Borderlands: The Pre-Sequel as the Devigorator, made by the "old" Hyperion.