The Lower

The STT-15 was born out of a desire to develop a true ambidextrous AR-15 pattern weapon system, built to the tightest possible tolerances. The full suite of ambidextrous controls comes standard on all Pillar AMBI receiver sets and lowers, and allows for standard manual of arms from both the right- and left-handed operation of the weapon.    

We machine the STT-15 directly from a billet of 7075-T651 aerospace grade American aluminum on our brand-new Haas CNC machinery. This allows us to hold ultra-tight tolerances and make sure that the final product is exactly as designed, and weigh in at only 1 Lbs.3.4oz. The finished receiver is then finished in Mil-Spec, MIL-A-8625 Type III hard anodizing.

Our philosophy with everything we do is simple. It has to work. Every time. The STT-15 is proof that you don’t have to sacrifice form to gain function. Our workhorse receivers are built from the ground up for reliable hard use functionality, and they look good doing It too.  

The Upper

Our approach to the AR-15 upper receiver is that it needs to stand out from the crowd of existing offerings while offering improvements and features not seen elsewhere. Our upper needed to be lighter, stronger, and different, and have the looks to turn heads. Our receiver truss pockets are usually the first thing people see. These distinctive trusses help to bolster the integrity of the receiver and give the functional style our customers demand. 

The STT-15 comes standard with M4 feed ramps and shell deflector. Our forward assists are retained by a threaded dowel pin to eliminate the use of a roll pin, and come with a milspec ejection port cover. The top picatinny rail features machined in T markings for easy optic relocation. 

When most people think of a billet receiver they think of a blocky, heavy, thick design that is CNC machined. We wanted to break that pattern. Our receivers are Cut from a single billet 7075 -T651 aerospace grade aluminum. Thru the use of 3D CAD modeling software, we were able to save weight in places that extra material didn’t have a purpose, such as the forward assist block and the shell deflector. These spots are often very bulky on other billet sets due to the difficulty of removing material on all of those angles. After all of was said and done the new STT upper receiver came in at only 8.2 ounces. 

Features:

• – Huge 1.38” Integrally Machined Magazine Well Flare
• – Ambidextrous Quick Attach Detach Sling Swivel Points With Anti-Rotation Stops Every 45 Degrees.
• – Ambidextrous Bolt Release.
• – Ambidextrous Magazine Release.
• – Bullet Pictogram Safety Selector Markings.
• – Set Screw Trigger Creep Adjustment.
• – Set Screw Upper Take Down Tension Adjustment.
• – Shooter Ready Finger Rest.
• – Oversized Winter Trigger Guard.
• – Dowel Screw Assembly.
• – Ultra Grip Texture On All Controls.

Specifications:

• Model: STT-15 
• Caliber:  5.56 NATO .223 REM, 300 BLACKOUT, 22LR, Multi-Cal
• Action: Semi-Auto
• Weight: 9.4 Ounces With Ambidextrous Controls 8.4 Ounces Without Ambidextrous Controls.
• Dimensions: Length: 7.69” Width: 1.490” Height: 4.015”
• Material: Billet 7075-T651 Aerospace Grade Aluminum, Cast A-2 Tool Steel
• Butt-Stock: Works With Any Mil-Spec or Commercial Buffer Tube and Stock.
• Magazine Compatibility: The Pillar is compatible with all STANAG pattern M16/AR15 magazines.
• Component Compatibility: Works With All Mil-Spec AR-15M16 Components*.

*Excluding proprietary ambidextrous controls.