Kastle XPS-226 Optic Riser: Absolute Co-Witness Setup Guide

By Shop Tactical Gear & Holsters丨Guerrilla Tactical | Published: 2026-10-26

Category: How-to Guides

Learn how to install the Kastle XPS-226 optic riser for an absolute co-witness setup. Step-by-step guidance, common mistakes, and practical tips.

Quick Answer

To achieve an absolute co-witness with your red dot, mount the Kastle XPS-226 optic riser on a Picatinny rail, then attach your optic and align the dot with your iron sights. This riser's 2.26-inch centerline promotes a heads-up posture for faster target acquisition.

Why Absolute Co-Witness Matters

Absolute co-witness means the red dot aligns perfectly with your iron sights when viewed through the optic. This setup allows you to use either the dot or the irons without shifting your head position, which is especially useful if the optic fails.

The Kastle XPS-226 riser is designed specifically to achieve this height on most AR-style platforms. Its 2.26-inch optical centerline is a common height for absolute co-witness, but you should verify your specific firearm and sight combination.

What You Need Before You Start

Gather the following: the Kastle XPS-226 riser, a Picatinny rail (M1913) on your firearm, your red dot optic, and a torque wrench with the appropriate bit for your mounting screws. Having a clean, dry rail is essential for a secure fit.

The riser is made of Type III hard anodized 7075 aluminum, so it is durable and lightweight at just 3 ounces. This makes it a solid choice for builds where weight matters.

Step-by-Step Installation for Absolute Co-Witness

Step 1: Prepare the Firearm: Ensure the firearm is unloaded and safe. Clean the Picatinny rail to remove any dirt or oil that could affect the mount's grip. Skipping the cleaning step can lead to a loose mount over time.
Step 2: Mount the Riser: Place the Kastle XPS-226 riser on the rail, aligning the slots with the rail teeth. Hand-tighten the mounting screws, then use a torque wrench to tighten to the manufacturer's recommended specification (typically 15-20 in-lbs, but check your manual). Over-tightening can strip the screws or damage the rail; under-tightening can cause the riser to shift.
Step 3: Attach Your Red Dot Optic: Mount your red dot optic onto the riser using the optic's mounting screws. Again, tighten to the recommended torque, usually 15-20 in-lbs, but verify with your optic's manual. Ensure the optic is seated flat against the riser to avoid canting.
Step 4: Align the Dot with Iron Sights: With the firearm pointed in a safe direction, look through the optic and adjust the windage and elevation until the red dot sits directly on top of the front sight post. This is your absolute co-witness. If you cannot achieve alignment, double-check that the riser is level and the optic is not canted.
Step 5: Verify and Test: Cycle the action (if applicable) and do a function check. Confirm the dot stays aligned after a few rounds or dry-fire exercises. Re-tighten if needed. A loose mount can cause zero shift; always re-check after the first range session.

Product Facts

Kastle XPS-226 Optic Riser - Absolute Co-Witness: The Kastle XPS-226 optic riser offers a 2.26-inch optical centerline height and uses patented KASTLE mounting tech. This height is designed to promote a heads-up posture, which can improve target acquisition speed and comfort during extended use.
Kastle XPS-226 Optic Riser - Absolute Co-Witness