The Trijicon ACOG RCO A4CP 4x32 Rifle Scope Chevron Dual-Illuminated Red Reticle (SKU TA31RCO-A4CP) is the USMC Rifle Combat Optic for the full-length M16A4: a fixed 4x, 32 mm ACOG with a red chevron bullet drop compensating reticle cut for a 20 in barrel, lit by fibre optics in daylight and a tritium lamp after dark with no battery of any kind.
How It Compares
This is the long-barrel member of the RCO family, quoted for hit probability out to 875 yd (800 m), and the only one of the three that ships with the TA53A thumb screw for mounting to a carry handle. The RCO M4CP is the same optic cut for the 14.5 in M4 and M4A1, and the RCO M150CP is the US Army M150 version, also cut for 14.5 in. The commercial equivalent, without the service accessories, is the ACOG 4x32 Chevron .223 BAC. Browse all rifle scopes, the Trijicon ACOG rifle scopes range or the full Trijicon optics range.
Ideal For
- Full-length M16A4-pattern rifles with a 20 in barrel, where the reticle holds are cut to that barrel
- Carry-handle rifles, using the supplied TA53A thumb screw
- Shooters who want the issued USMC specification rather than the commercial equivalent
Key Features
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Reticle: Red Chevron BDC, USMC Rifle Combat Optic for the M16A4 full-length rifle; hit probability out to 875 yd (800 m)
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Illumination: Dual illuminated: fibre optics (day) + tritium (night); battery-free
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Calibre Calibration: .223 / 5.56, calibrated for a 20 in barrel
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Mount: Flattop Thumbscrew Mount TA51 (included); TA53A thumb screw for carry-handle mounting
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Warranty: Trijicon Limited Lifetime Warranty
Technical Specifications
| Magnification / Objective |
4x fixed |
| Objective |
32 mm |
| Reticle |
Red Chevron BDC, USMC Rifle Combat Optic for the M16A4 full-length rifle; hit probability out to 875 yd (800 m) |
| Reticle Colour |
Red |
| Calibre Calibration |
.223 / 5.56, calibrated for a 20 in barrel |
| Illumination |
Dual illuminated: fibre optics (day) + tritium (night); battery-free |
| Eye Relief |
1.5 in (38 mm) |
| Exit Pupil |
0.32 in (8.1 mm) |
| Field of View |
36.8 ft at 100 yards (12.3 m at 100 m); 7° |
| Weight |
14.9 oz (422 g) with the TA51 mount |
| Housing |
Forged aluminium (7075-T6), matte black |
| Mount |
Flattop Thumbscrew Mount TA51 (included) |
| Water Resistance |
Submersion depth 66 ft (20 m); dry-nitrogen filled, fogproof |
| What's Included |
RCO, TA51 thumbscrew flattop adapter, TA53A thumb screw for mounting to a carry handle, TA91 killFlash anti-reflection device, TA96 Scopecoat, TA56 LensPen, TA71E lanyard assembly, PR15 logo sticker |
| SKU / MPN / UPC |
TA31RCO-A4CP / TA31RCO-A4CP / 719307302068 |
Warranty
Trijicon back this with their Limited Lifetime Warranty: the optical system and metal structure are covered against defects in materials and workmanship for the lifetime of the original owner. The tritium lamp carries its own multi-year term from date of manufacture.
UK Delivery & Support
Delivery is a flat £5 by Royal Mail Tracked 24, UK addresses only, with no free-delivery threshold. Allow 7–10 business days from order to doorstep — most of that window is sourcing, and the Tracked 24 leg is the last day of it. Duties and import fees are prepaid, so there is nothing to pay on arrival. Questions about reticles, mounts or fit? Email info@xtremetactical.co.uk, or message us on WhatsApp or by text on +44 7940 435857 — messages only, we don't answer voice calls.
Frequently Asked Questions
Does it need batteries?
No — the reticle is lit by fibre optics in daylight and tritium in the dark. There is nothing to switch on and nothing to run flat.
What calibre is the reticle calibrated for?
.223 Remington and 5.56 NATO, with the holds cut for a 20 in barrel. On a 14.5 in carbine the holds will be short.
Can I mount it on a carry handle?
Yes — the TA53A thumb screw supplied with this configuration is for carry-handle mounting, and the TA51 flattop adapter is included for a rail.
What is the difference between the A4CP and the M4CP?
Barrel length. The A4CP reticle is cut for the 20 in M16A4, the M4CP for the 14.5 in M4 and M4A1. The optics are otherwise the same.
Can I shoot with both eyes open?
Yes — the ACOG is designed around the Bindon Aiming Concept for both-eyes-open shooting at speed.
What warranty does it carry?
Trijicon's Limited Lifetime Warranty. The tritium lamp carries its own multi-year term from date of manufacture.
Is this a genuine Trijicon product?
Yes — factory-new, genuine Trijicon, covered by Trijicon's Limited Lifetime Warranty.
