Trijicon ACOG TA31RCO 4x32 Rifle Combat Optic
- Magnification Minimum: 3x
- Objective Lens Diameter: 40 mm
- Night vision: No
- Thread Type: UNC
Last refreshed Jun 22, 2026 · Based on the Amazon listing and published specifications, not hands-on testing.
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ASIN: B0014VVSAAModel: ACOG TA31RCO-A4CPCategory: Rifle Scopes
More from this brandAll Trijicon rifle scopesOverview
The Trijicon TA31RCO-A4CP ACOG is a fixed 4x32 rifle scope built to USMC specification for the M16A4 platform, using a tritium and fiber optic illuminated reticle that needs no battery. The reticle is a bullet drop compensating design calibrated for a 20 inch barrel out to 800 meters.
- 4x32 fixed magnification
- Tritium and fiber optic illuminated reticle, no battery
- USMC-spec bullet drop compensating reticle to 800m
- Includes TA51 mount for A4 uppers
Who it's for
Built for someone assembling an A4-pattern rifle who wants the same optic used in Marine Corps service, particularly if the rifle has a 20 inch barrel matching the reticle's calibration. Less relevant for a shorter-barrel AR build, since the bullet drop reticle is tuned to the A4's ballistics.
Pros and cons
- Battery-free tritium and fiber optic illumination
- Reticle calibrated for 800 meter bullet drop on a 20 inch barrel
- Forged 7075-T6 aluminum housing
- Backed by lifetime warranty
Performance notes
Trijicon backs the optic with a lifetime warranty, and one reviewer who had a zeroing issue found it was a bad barrel rather than a scope fault after sending it in for evaluation.
Specifications
| Brand | Trijicon |
|---|---|
| Model | ACOG TA31RCO-A4CP |
| Dimensions & fit | |
| Objective Lens Diameter | 40 mm |
| Construction & materials | |
| Color | Red |
| Included components | |
| Unit Count | 0.06 pounds |
| Included Components | Optic |
| Other details | |
| Magnification Minimum | 3x |
| Night vision | No |
| Thread Type | UNC |
| Sport Type | Hunting |
Frequently asked questions
What barrel length is this reticle calibrated for?
It is designed for the USMC M16A4 with a 20 inch barrel, with bullet drop compensation out to 800 meters.
Does it require a battery?
No, illumination comes from a tritium and fiber optic combination that adjusts automatically to ambient light.