This unnamed Duke Arms Company assault sniper rifle is due to appear in Grand Theft Auto VI, seen in an official screenshot resting across a poacher's leg aboard his airboat, with a Duke-branded engraving visible above the magazine. It appears to be a longer-barreled, sniper-oriented variant of the Duke carbine, sharing an almost identical stock, magazine, and barrel profile, and its overall look has been compared to a real-world M4A1 Block II fitted with a 20-round STANAG magazine. No further specifications, such as caliber or capacity, have been confirmed.
Weapon data via GTA Wiki (Fandom), CC BY-SA 3.0.