ERA-TAC Angle Cosine Indicator (ACI)

• Angle cosine compensation: The ACI helps account for the trajectory change that occurs on steep uphill or downhill shots, making hold or correction decisions more consistent at longer distances.
• Integrated bubble level: The built-in level helps reduce cant error, which is especially important when small rifle tilt can shift point of impact during precision shooting.
• Visible while aiming: The indicator is positioned so the red needle remains easy to read in the shooting position, allowing fast angle reference without breaking concentration behind the riflescope.
• UNIVERSAL-Interface compatibility: Designed for the ERATAC interface system, it adds angle and level information without forcing a change to scope position, which keeps an established rifle setup intact.
• Compact aluminum construction: The light 30.00 g aluminum body adds useful ballistic support with minimal extra weight, so the rifle remains practical for field or duty use.

About the ERA-TAC Accesories Series

ERA-TAC Accesories form part of the ERATAC family introduced for the civilian market and law-enforcement use in 2010. Within the brand’s lineup, this series covers the supporting components that expand a rifle setup beyond the basic mount, including adapters, interface parts, sling-related hardware and specialized shooting aids. The common idea behind the range is modularity: accessories are built to integrate with the ERATAC mounting system so the rifle can be configured for a specific task without unnecessary bulk or permanent modification.

In practical terms, the series is aimed at shooters who need more than simple scope attachment. It supports tactical optics, precision rifles and field rifles that may require add-on capability for lasers, lights or angle-related shooting tools. One of the distinguishing elements in the range is the use of the UNIVERSAL-Interface, which allows accessories to be attached in a controlled and repeatable way. The series also includes the angle cosine indicator, developed to help compensate for gravity effects on uphill and downhill shots, while its accompanying bubble level helps confirm that the firearm is held level before the shot breaks.

About the ERA-TAC Angle Cosine Indicator (ACI)

The ERA-TAC Angle Cosine Indicator (ACI) is a compact shooting aid for riflescope-equipped rifles where steep shot angles can change the effective ballistic solution. Instead of treating an uphill or downhill shot like a level-distance shot, the ACI gives the shooter a fast visual reference for angle compensation, helping translate ballistic data into a more realistic correction. This makes it especially relevant for long-range, mountainous terrain, elevated positions and other situations where line-of-sight distance and true ballistic distance are not the same.

The design combines an angle cosine indicator with a bubble level, so it addresses two common precision-shooting problems at once: angle error and rifle cant. The level helps keep the rifle upright, reducing lateral point-of-impact shift that can become more noticeable as distance increases. ERATAC also places the indicator so the red needle remains visible while aiming, which is useful when the shooter needs to confirm angle information without coming off the gun. Because it mounts through the ERATAC UNIVERSAL-Interface, it can be added without changing the scope position, preserving eye relief and the overall balance of an established rifle setup. Its aluminium construction and low 30.00 g weight keep the accessory unobtrusive while still making it suitable for serious field use.

About ERA-TAC

ERA-TAC is a brand of Recknagel GmbH & Co. KG, based in Bergrheinfeld, Germany. Recknagel was founded in 1867 in Albrechts near Suhl, Thuringia, and has long produced accessories for hunting, sporting and tactical firearms. The ERATAC line was introduced in 2010 to focus on tactical mounts and related accessories for civilian and military markets. Across the range, the brand is known for riflescope mounts, Picatinny rails, backup sights and weapon accessories built around practical modularity. ERATAC products are typically machined from solid aluminum and hard-anodized to Mil-Spec Type III, reflecting the brand’s emphasis on robust construction and repeatable mounting performance.

Main Features

• Manufacturer: ERA-TAC
• Series: ERA-TAC Accesories
• Made in: Germany
• Weight: 30.00 g
• Material: Aluminium
• Intended for: Riflescopes
• Color: Black

Warranty

ERA-TAC Angle Cosine Indicator (ACI) is covered by a 2-year warranty.