the author of this weapon is CSEPteam, one of my favorites guns on nexus actually. i had not part in making this weapon, just ported it.
From the author:
A new lore friendly bullpup assault rifle based on the Fallout 3 R91 Assault Rifle with plenty of attachments and custom animations.
Injected after level 10 around the wasteland only on gunners.
Unique found in a custom dungeon in the glowing sea, a misc quest should lead you to the location, small key puzzle and a bit of combat awaits you.
CREDITS:
WarDaddy/Comrade Bear - Animations
The Kruseman - Assets
Degenerate Dak - Also Assets
a_blind_man and Dank Rafft - LL Inject Script
Pigness (AUTHOR) - Everything Else
Screenshots: Pigness