Geissele's Super Duty Mod 1 Upper Assembly in 8" .300 Blackout is the current evolution of the Super Duty platform — purpose-built for suppressed short-barrel work where .300 BLK earns its keep. Geissele's Phased Array Gas System is the headline feature: a patented gas port geometry that meters pressure for both supersonic and subsonic ammunition without an adjustable block, so the rifle cycles reliably suppressed or unsuppressed, subs or supers, with no tuning.
The complete upper ships with a Geissele cold-hammer-forged 8" .300 Blackout barrel, Geissele Super Modular Rail (SMR) Mk16, and Geissele's proven charging handle and bolt carrier group. Black Type III hardcoat anodize on the receiver, matching rail, and all hardware. Assembly is drop-on to any mil-spec lower.
This is not a parts-bin upper. Every component is Geissele-made to Geissele tolerances, which is why Super Duty rifles are on duty contracts with serious end users. If you are building a suppressed .300 BLK SBR or pistol for home defense, PDW role, or working dog, this is the upper that stops the conversation.
Order yours today and run Geissele end-to-end.
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