The San Tan Tactical STT-15 Pillar Upper Receiver (San Tan Tactical part no. STT-PILLAR-1) is a stripped billet upper built for 5.56 NATO and .223 Remington AR-15 builds that want a lighter, stiffer platform than a standard forged or blocky billet design. San Tan Tactical machines the receiver with a truss-pocket design that spreads stress across the whole platform like a bridge, instead of concentrating it right behind the barrel extension threads the way conventional uppers do. That added rigidity is aimed at improving accuracy while shaving weight compared to a typical thick-walled billet upper. It ships as a stripped receiver only, with a flat-top rail for mounting optics, and does not include a barrel, bolt carrier group, or lower receiver.

Key Specifications

• Machined from billet aluminum rather than forged for tighter tolerances.
• Uses a truss-pocket design that distributes stress across the platform instead of concentrating it at the threads.
• Engineered to be lighter than a conventional thick-walled billet upper.
• Added rigidity is intended to improve accuracy over standard billet designs.
• Includes a flat-top Picatinny rail for mounting optics.
• Built for 5.56 NATO and .223 Remington AR-15 builds.
• Finish: Type III hardcoat anodized for corrosion resistance.
• Machined with M4 feed ramps standard.
• Compatible with standard mil-spec AR-15 lower receivers and barrel nuts.

Frequently Asked Questions

Does this include a barrel or bolt carrier group? No, this is a stripped upper receiver only; it does not include a barrel, bolt carrier group, or lower receiver.

What is the truss-pocket design for? It spreads stress across the receiver like a bridge instead of concentrating it behind the barrel extension threads, adding rigidity while saving weight.

What caliber is this upper built for? It is built for 5.56 NATO and .223 Remington AR-15 builds.

Buy the San Tan Tactical STT-15 Pillar Upper Receiver

Start your next build on a receiver engineered to shave weight without giving up rigidity. Order it from our Lubbock, Texas gun shop and we will get it moving as soon as it is ready to ship, no FFL required since it ships as a stripped upper only. Shop more from San Tan Tactical or browse our AR-15 uppers selection to keep building.