Trijicon ACOG 4 x 32 Scope USMC Rifle Combat Optic for A4
- Rifle Scope
- 40 mm
- 3x
- Hunting
- Better rated than 77%
A durable, purpose-built optic for an A4 clone build, and reviewers with military experience on the same scope confirm it matches their issued units in construction and glass quality.
As an Amazon Associate, ProductDome may earn a commission from qualifying purchases made through links on this page.
How it ranks among the 359 rifle scopes we track
4.8★ across 87 Amazon ratings, Bayesian-smoothed toward the category average.
87 Amazon ratings, weighted on a log scale so huge counts don't drown everything.
Brand identity, imagery, description and spec coverage.
The ProductDome score is separate from the Amazon rating shown above: it combines the Bayesian-smoothed Amazon rating with evidence volume, tracked demand, and data quality across the 359 rifle scopes we track - how the scorecard works · full rifle scopes data report. Confidence: medium - useful but incomplete evidence.Last refreshed Jun 22, 2026. Data-computed, not a hands-on test. Compiled by the ProductDome Research Team.
Overview
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.
What buyers say
From Amazon customer reviews.
Several reviewers with Marine Corps or Army service background confirm this civilian CP-suffix version matches the construction and glass quality of the optics they were issued, describing it as durable enough to trust in the field. One reviewer had a zeroing problem and found through Trijicon's warranty service that a bad barrel, not the scope, was the cause, and noted having to pay return shipping despite the lifetime warranty covering the repair itself.
Strengths and trade-offs
Drawn from this product's published specifications.
- 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
The tritium and fiber optic illumination adjusts brightness with ambient light and needs no battery, which multiple reviewers with service experience confirm performs the same as their issued units. 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 | TA31RCO-A4CP |
| Dimensions & fit | |
| Objective Lens Diameter | 40 mm |
| Item Weight | 10.5 ounces |
| Construction & materials | |
| Material Type | Fiber Optics & Tritium |
| Color | Red |
| Compatibility & installation | |
| Mounting Type | A4 w/ TA51 Mount |
| Compatible Devices | Reticle Calibration: .223 / .308 / M193 / 300 BLK / 6.8 SPC |
| Included components | |
| Unit Count | 1 ounce |
| Included Components | Optic |
| Other details | |
| Magnification Minimum | 3x |
| Sport Type | Hunting |
| Reticle Type | Chevron Ranging |
| Thread Type | UNC |
| Night vision | No |
| Product Style | USMC Chevron for A4 |
Other Trijicon rifle scopes
How it compares
This product against the closest alternatives we track in rifle scopes.
| Product | Amazon rating | Ratings | ProductDome score |
|---|---|---|---|
| Trijicon ACOG 4 x 32 Scope USMC Rifle Combat Optic for A4This product | 4.8 / 5 | 87 | 4.2 / 5 |
| UTG 3-12X44 30mm Compact ScopeUTG | 4.5 / 5 | 3,000 | 4.4 / 5 |
| Vortex Optics Diamondback Second Focal PlaneBrand | 4.7 / 5 | 1,500 | 4.3 / 5 |
| PINTY Tactical Rifle Scope Combo: Illuminated OpticsPinty | 4.4 / 5 | 1,100 | 4.3 / 5 |
| Firefield RapidStrike 1-6x24 SFP Riflescope KitFirefield | 4.5 / 5 | 900 | 4.3 / 5 |
Similar rifle scopes from other brands
Questions about the Trijicon TA31RCO-A4CP
Common buyer questions answered straight from the product spec data - no fluff, no "it depends".
What does the CP in TA31RCO-A4CP mean?
CP denotes the civilian production version of this optic, as opposed to the military contract version, according to reviewers familiar with both.
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.