Trijicon ACOG 4x32 Rifle Scope Crosshair .223 BAC Red Reticle with RMR Red Dot Sight – TA31-C-100550

The Trijicon ACOG 4x32 Rifle Scope Crosshair .223 BAC Red Reticle with RMR Red Dot Sight (SKU TA31-C-100550) is a factory two-optic package: a fixed 4x magnification, 32 mm objective ACOG prism rifle scope with an etched crosshair bullet drop compensating reticle calibrated for .223/5.56 and red battery-free illumination, with a Trijicon RMR miniature red dot sight pre-mounted above it.

The pairing solves the one thing a fixed-power ACOG cannot do on its own. The ACOG gives you 4x magnification and a calibrated bullet drop reticle for identification and holds at distance; roll the rifle onto its side and the RMR gives you a 1x red dot for anything close and fast. Neither optic depends on the other: the ACOG reticle is etched into the prism and lit by fibre optic and tritium with no battery, and the RMR runs its own LED from its own cell.

Trijicon designed the ACOG — Advanced Combat Optical Gunsight — for military service, and the RMR — Ruggedized Miniature Reflex — alongside it. That heritage is engineering, not marketing: forged aluminium housings on both optics, a waterproof seal, and a magnified sight that has nothing to switch on.

Illumination Colour: Red — the same package is also stocked as the ACOG 4x32 Crosshair .223 BAC Green reticle with RMR red dot sight (TA31-C-100552).

How It Compares

This is the ready-built version of the Trijicon ACOG 4x32 rifle scope Crosshair .223 BAC Red reticle, with the RMR already fitted, so there is no separate mount to source or zero from scratch. The other reticle offered in the same package is the ACOG 4x32 Chevron reticle with RMR red dot sight (TA31-D-100549). Prefer a sealed, enclosed-emitter red dot on top instead of the open-emitter RMR? Trijicon builds that as the Trijicon ACOG 4x32 rifle scope with RCR red dot sight (TA31-C-100813). If you already own an ACOG and want to add your own RMR, the Trijicon RM35 RMR mount for ACOG (AC32007) and Trijicon RM66 RMR mount for ACOG (AC32029) are the Trijicon mounts that piggyback one above an ACOG with mounting bosses, matched to your ACOG model. See the whole range in Trijicon ACOG rifle scopes, the optics for straight-pull rifles, the wider offset and secondary red dot sights and the full Trijicon optics range, or read our guide to prism scopes and Trijicon buyer's guide.

Ideal For

• Civilian Service Rifle and practical rifle shooting where one stage mixes close targets with 200 m and 300 m detail
• Practical shotgun, 3-Gun and multi-discipline straight-pull carbine shooting, rolling from magnified to 1x without changing optics
• Shooters who want the magnified sight to keep working whether or not any battery does
• Airsoft and milsim builds replicating an issued rifle with a piggyback red dot

Key Features

• ACOG Reticle: BAC .223 Crosshair — etched into the prism, calibrated for .223/5.56, Red illumination
• ACOG Illumination: Fibre optic and tritium, battery-free — daylight feeds the fibre and tritium lights the reticle in darkness
• Secondary Sight: Trijicon RMR miniature red dot sight, battery-powered LED, pre-mounted above the ACOG
• Magnification / Objective: 4x magnification, 32 mm objective on the ACOG; 1x on the RMR
• Aiming Concept: Bindon Aiming Concept (BAC) for both-eyes-open shooting at magnification
• Eye Relief: 1.5 in (38 mm) on the ACOG
• Field of View: 36.8 ft at 100 yards (12.3 m at 100 m)
• Housing: Forged aluminium, waterproof
• Origin: Made in USA

Technical Specifications

What's Included

• Trijicon ACOG 4x32 rifle scope (TA31-C-100550)
• Trijicon RMR red dot sight, pre-mounted
• Integrated mount
• Lens covers
• User manual
• Warranty documentation

Warranty

Covered by Trijicon's manufacturer's warranty. Keep your order confirmation as proof of purchase and register the optic with Trijicon after fitting; we handle warranty claims for you from the UK.

UK Delivery & Support

UK-stocked and dispatched tracked from our UK warehouse — no import duties or customs delays — backed by UK-based support and Trijicon's warranty.

Frequently Asked Questions

Does the Trijicon ACOG 4x32 need batteries?
No — the ACOG half of this package is battery-free. A fibre-optic light pipe along the top of the housing collects ambient daylight and feeds it into the etched reticle, and a sealed tritium lamp illuminates the same reticle in darkness. The RMR red dot mounted above it is a separate, battery-powered LED sight, so the magnified optic keeps working regardless of the dot.

What is the Bindon Aiming Concept (BAC) on a Trijicon ACOG?
The Bindon Aiming Concept (BAC) is Trijicon’s name for shooting an illuminated ACOG with both eyes open. The reticle is bright enough that the brain favours the magnified sighting eye for the aiming point while still using the unmagnified view from the other eye, so you keep close-range speed and situational awareness at 4x magnification.

Which calibre is this ACOG reticle calibrated for — .223 or .308?
This Trijicon ACOG 4x32 (TA31-C-100550) is calibrated for .223/5.56: the bullet drop compensating stadia below the crosshair aiming point correspond to that cartridge. Trijicon calibrates the ACOG for .308/7.62 in the larger 3.5x35 body instead — see the Trijicon ACOG rifle scopes collection.

Is the RMR red dot already fitted to the ACOG?
Yes — this is a factory package and the Trijicon RMR is supplied pre-mounted above the ACOG, so you do not need to buy a separate RMR mount. Both optics still need zeroing to your own rifle and load.

What is the eye relief on the Trijicon ACOG 4x32?
The Trijicon ACOG 4x32 has 1.5 in (38 mm) of eye relief. That is short by rifle scope standards and typical of a compact prism optic, so it wants a consistent cheek weld and a mounting position that puts your eye close to the ocular.

What happens to the aiming point if the ACOG illumination is not visible?
The ACOG reticle is etched into the prism glass rather than projected, so the full crosshair aiming point and its bullet drop stadia remain black and usable against a bright background even when the tritium and fibre-optic illumination is not contributing.