The Trijicon ACOG TA31RCO-M855 (model TA31D100581) is an Advanced Combat Optical Gunsight built for the USMC M16A4 (20-inch barrel) or M4 (14.5-inch barrel) weapon systems, using dual illumination technology that combines fiber optics and self-luminous tritium.

Key Specifications

• Magnification: 4x
• Objective Lens: 32mm
• Reticle: Dual-illuminated red chevron, calibrated for M855 ammunition (RCO BDC)
• Illumination: Fiber-optic (daylight, self-adjusting) and tritium (darkness), no batteries needed
• Weapon Fitment: USMC M16A4 (20-inch barrel) or M4 (14.5-inch barrel)
• Shooting Style: Both-eyes-open engagement for full situational awareness
• Manufacturer: Trijicon

Frequently Asked Questions

What rifle is the TA31RCO-M855 built for?
It’s built for the USMC M16A4 with a 20-inch barrel or the M4 with a 14.5-inch barrel.

Does the RCO’s illuminated reticle need batteries?
No, it combines fiber optics for daylight brightness adjustment with self-luminous tritium for total darkness, so it never needs batteries.

Buy the Trijicon ACOG TA31RCO-M855 Today

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