4-2. RAIL INTERFACE SYSTEM

a. The RIS may be removed for cleaning in the same manner as

handguard slip ring and pivot the upper and lower RIS assemblies off the front handguard retaining cap.

Figure 4-3. Remove RIS Assembly.

CAUTION

If the upper RIS is removed without first loosening the screw at the muzzle end, components may be damaged.

b. Attachment and Detachment of the Rail Interface System.

(1) Handguard sections can be quickly attached and detached from the RIS. A spring latch at one end of each handguard section auto-matically engages cutouts in rail recoil grooves #1 or #15 (depending on its orientation). To slide a handguard section beyond a cutout, or to remove it, slide it in the desired direction while applying thumb pressure to the center of its spring latch.

Figure 4-4. RIS Handguard Sections.

(2) To cover the side and bottom quadrants, install the hand-guard sections from the muzzle end of the RIS. To cover the top quad-rant, install the handguard sections from the rear of the upper receiver group with the carrying handle or sighting system removed.

(used on rails partially occupied by accessories) should be oriented with their spring latches away from the accessories.

(4) Nine handguard sections of various lengths are provided with the RIS. They are:

Four full length (6.15”) sections

Two 3.9” (approximately help length) section One 2.65” (medium short length) section

Two 1.65” (approximately one-third length) sections

For ease of reference, the three shorter lengths can be referred to by the number of ribs along their outer surfaces: “6 rib,” “4 rib,”

or “2 rib.” See figure 4-17.

Figure 4-5. Install Handguard Sections from Muzzle End.

4-3. ENHANCED COMBAT OPTICAL SIGHT-NAVY.

Enhanced Combat Optical Sight-Navy (ECOS-N) is a variable intensity, non-magnifying, day optical sight designed for close combat. It allows very fast target acquisition and engagement at short ranges, while still providing enhanced aiming out to 300 meters as compared to iron sights.

The aiming dot is powered by a lithium battery with a manufacturer esti-mated life of 100-1000 hours.

The sight uses a projected red dot collimator, that when zeroed, creates an optical axis that is aligned with the bore and uses reflective coatings on the lens to generate an aiming dot image that appears to be out at the target rather than on the lens. Since this sight is a collimator the dot remains well aligned with the bore no matter from what angle it is viewed

enhances the situational awareness and the speed and ease of acquiring and tracking targets.

Figure 4-6. ECOS-N.

a. ECOS-N Installation.

(1) Battery Installation: Remove battery cap and install battery with positive (+) end towards cap. Inspect the O-ring to be sure it is present and not damaged. Failure to do so could result in water leakage into the battery compartment. Reinstall battery cap - hand-tighten only.

ITEM DESCRIPTION

1 Battery Cap, Short

2 Cap, Adjustment (Windage/Elevation) 3 Cap, Rotary Switch

4 Lens Cover, Rear 5 Lens Cover, Front

(2) Installing the ECOS-N on the Mount: Remove the battery cap from the sight. Remove the four allen screws and cover from the mount, then replace with the sight in position and firmly tighten the screws. The windage and elevation adjustments should be to the top and right respectively. Reinstall the battery cap.

(3) Installing the ECOS-N on the Weapon: Ensure the rail and grabber are free of dirt, paint, and burrs to assure a repeatable zero.

Position the sight and mount on the rail, then hand tighten plus 1/4 turn the rail grabber knob, figure 4-20. The knob should be to the left of the carbine. Ensure there is space between the bottom front part of the sight and the top of the base/weapon. It is recommended that the sight be placed at the furthest forward position on both the receiver and the rail interface system. Placing the sight too far back will obscure the shooter’s peripheral vision. For the best zero retention, always place the mount into the same slot on the rail.

b. ECOS-N Operation. Zeroing.

CAUTION

Do not continue to adjust windage and elevation mecha-nisms if resistance is encountered. This could result in

damage to equipment.

(1) Sight Zero: The ECOS-N is mechanically zeroed at the fac-tory. If the sight is properly installed, only small adjustment should be necessary. The, per click, windage and elevation adjustments are set at 1/2 inch at 100 yards, or 13 millimeters at 100 meters. After initial firing, check to ensure the mount and sight are still secure. After completion of zero turn selector switch to OFF and close lens covers.

the front sight post. Then add eight clicks of adjustment in the up direc-tion to compensate for the addidirec-tional height of the ECOS-N above the front sight post. This method will give satisfactory performance to 100 meters. Beyond 100 meters the sight should be zeroed by live fire.

(3) Point of Aim: The aiming dot in the reflex sight appears to be approximately 4 to 5 minutes of angle. This means that as the range increases, the aiming dot appears to cover a larger portion of the target.

See Figure 4-8 for relationship of Range, Aiming DOT, and M855 Projec-tile Trajectory.

(4) Night Operation: The ECOS-N has 10 red dot intensity set-tings. Four of these are suitable for use with night vision devices. The higher settings are visible through the front of the sight and could give away your position.

NOTE

At higher intensity settings the red dot is visible through the front of the sight.

(5) Operation Under Extreme Conditions:

(a) Extreme Heat: No special procedures required.

(b) Extreme Cold: Could shorten battery life. Keep extra batteries warm.

(c) Sea Spray, Water, Mud and Snow: Ensure battery cap and two adjustment screw caps are hand tightened before exposure or submersion. Clean lenses as soon as possible after exposure.

(d) Dust and Sand Storms: Keep lens caps closed.

(e) High Altitudes: No special procedures required.

c. ECOS-N Maintenance.

(1) Care & Cleaning: Clean the lens of dust or salt by rinsing it in fresh water. Shake or blow out excess water and dry the lens with a clean and soft cloth. To avoid scratching the lens, rinse all particles from the lens fully before wiping it with the cloth. The lens should never be

returned to the Program Office and replaced per instructions in Annex A of ST-23-31-1.

(3) Repair Parts List: A list of repair parts is contained in Annex A of ST-23-31-1. All listed parts can be installed at the operator or unit level. Special tools or equipment are not required.

(4) Storage: The ECOS-N is listed in Registry as a serialized item. It should be stored in accordance with applicable service physical security instructions. Remove battery and allow lenses to dry before stor-age. Keep lens caps closed when the sight is not in use.