Carrier Assembly: The flared rear of the enhanced bolt carrier is designed to reduce carrier tilt/cant during recoil and increasing reliability by strategically relocating key bearing surfaces.

The STT enhanced carrier has fewer points of contact resulting in less friction area and the increase in mass ensures proper gas pressures and increases dwell time, thus improving extraction while shooting suppressed or short-barreled rifles (SBRs)

• Case-hardened 8620 steel (complete care is taken during the heat treat process, so as to not harm the metal).
• 3 forward ports enlarged to allow overpressure to escape.
• Optimized for suppressor use.
• Black Nitride Finish.
• 4130 Steel, attached with Grade 8 hardware, torqued and properly staked into a milled “valley” around a fully encased ejection port area, for added strength and rigidity.
• Hardened 4340 cam pin.
• Fully chamfered cam pin channel.
• Mil-Spec firing pin made of AISI 8740 steel, center-less ground and Hard Chrome coated.

Bolt Assembly: The Bolt is “true” Mil-Spec dimension and external surfaces are CNC ground after heat treat for a precision fit. The bolt is machined to AR-10 .308/6.5 Creedmoor. STT bolts are held to the highest possible tolerance possible. Outside critical dimensions held to .0005”. The “trumpet” area behind the gas rings, where carbon normally collects, is precision CNC Ground after heat treatment, to ensure as smooth of an area as possible, easing clean up, and longevity.

• 9310 Case Hardened Steel.
• All Bolt components Shot Peened & Black Nitride coated.
• 4340 Steel, Manganese Phosphate coated.
• Magnetic Particle Inspected (MPI) and High Pressure Tested (HPT).
• Black Nitride low friction coating.
• Mil-Spec Billet Extractor Spring & CRANE O-Ring Upgrade.
• AR-10 .308/6.5 Creedmoor Specific.

BLACK NITRIDE is a process commonly referred to anonymously with SBN (Salt bath nitride) and sometimes QPQ (quench polish quench).  All of these are a form of nitrocarburizing which is a chemical hardening of steel in short.  

Black Nitride Finish Benefits

• Increased wear resistance
• Improved fatigue strength
• Exceptional lubricity and low friction coefficient.
• Withstand corrosion per ASTM spec B117
• Improved lubricity
• Enhanced cosmetic appeal
• Better corrosion protection at an equivalent or lower cost than hard chrome-nickel plating

Like all San Tan products, this is exceptionally well made, much more durable than the standard Mil-Spec AR15 BCG and includes STT’s Satisfaction Guarantee and Lifetime Warranty.