All San Tan Tactical STT-15 and 6ARC rifles are engineered from the ground up with one thing in mind: Reliability. Every part of the rifle has been thoughtfully curated to work in concert to deliver an attractive workhorse. The heart of our rifles is of course the flagship Pillar billet receiver set made of 7075 T6 aerospace grade aluminum featuring a full suite of ambidextrous controls including bolt releases and magazine releases.