DRAFT TC-23-AIMSS CHAPTER 1 RAIL ADAPTER SYSTEM 1-1 DESCRIPTION The Rail Adapter System (RAS) consists of a set of lightweight specially modified sections that replace the standard front handguards on the M4 carbine. It is a key part of the Adapter kit that provides a secure mounting point for the various other components, except for those that must be mounted directly to the rail on the upper receiver. 1-2 CHARACTERASTICS Length: 6.62 in. Width: 2.59 in. Weight: 11 oz. Rails: Extruded 6061 T6 Aluminum Black Hard Anodized Coating Rail Covers/Heat Shields: Glass-filled nylon 1-3 COMPONENTS Figure 1-1, Rail Adapter System Components 1-1
DRAFT TC-23-AIMS 1-4 SAFETY 1-2, Rail Covers / Heat Shields WARNING Confirm that the weapon is unloaded and on SAFE before performing these steps. Rotate the selector to the safe position. Remove the magazine. Draw the bolt/carrier assembly to the rear and visually inspect the chamber and receiver. Close the bolt/carrier assembly. Confirm that the selector is set to SAFE, and close the ejection port cover. WARNING When firing the weapon at high rates of sustained fire the barrel and metal components of the RAS can become hot enough to inflict serious burns. Cover exposed metal portions of the rail with the plastic rail covers. Use the Forward Hand Grip during heavy sustained fire. WARNING Do not exceed the sustained rate of fire (12-15 rounds per minute) for the M4 Carbine. Overheating will result in "cook offs"(160rds) or the barrel can soften and burst (540rds). 1-2
DRAFT TC-23-AIMSS 1-5 INSTALLATION AND REMOVAL OF THE RAIL ADAPTER SYSTEM a. Remove the standard handguards as in routine field stripping by compressing the rear handguard slip ring and pivoting the handguards off the front handguard retaining cap. Refer to Army Technical Manual (TM) 9-1005-319-23P (May 1991), or Air Force Technical Order (TO) 11 W3-5-5-42 (May 1991) for detailed field stripping instructions. Figure 1-3 Removing Standard Handguards b. Orient the upper RAS properly by confirming that the arrow on its inner surface points towards the muzzle of the carbine and secure to the weapon. Figure 1-5 Orientation of Top RAS Assembly d. Install the upper RAS assembly in the same manner as a standard upper handguard. Confirm that the latch at the muzzle end of the Top RAS rail rests on top of the front 1-3
DRAFT TC-23-AIMS handguard retaining cap, and that the forward lip of the RAS rests within it. Compress the rear handguard slip ring and pivot down the upper RAS assembly. Figure 1-6 Installation of Upper RAS Assembly e. Release the rear handguard slip ring and confirm that it engages around the rear flange of the upper RAS assembly. Two small pins automatically lock the Adapter with scallops in the barrel nut to prohibit rotation of the RAS. This helps to retain the zero of those accessories mounted on the upper rails. f. Orient the lower RAS assembly under the barrel by confirming that the arrow on the liner's inner surface points towards the muzzle of the carbine. Do not remove the thermal liner from the lower RAS assembly. Figure 1-7 Orientation of the Lower RAS Assembly h. Install the lower RAS assembly in the same manner as a standard lower handguard. Compress the rear handguard slip ring and pivot up the lower RAS assembly. 1-4
DRAFT TC-23-AIMSS Figure 1-8 Installation of Lower RAS Assembly i. Release the rear handguard slip ring and confirm that it engages around the rear flange of the lower RAS assembly. j. The RAS may be removed in the same manner as standard Compress the rear handguard slip ring and pivot the upper and lower RAS assemblies off the front handguard retaining cap. Figure 1-9 Removing Upper and Lower RAS Assemblies 1-5
DRAFT TC-23-AIMS k. ATTACHMENT AND DETACHMENT OF THE RAIL ADAPTER SYSTEM. (1) The rail covers / heat shields can be quickly attached and detached from the RAS. A spring latch at one end of each rail covers / heat shields automatically engages cutouts in rail recoil grooves #1 or #15 (depending on its orientation). To slide the rail covers / heat shields 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 1-10 Location of the Spring Latch (2) To cover the side and bottom quadrants, install the rail covers / heat shields from the muzzle end of the RAS. To cover the top quadrant, install the rail covers / heat shields from the rear of the upper receiver group with the carrying handle or sighting system removed. (3) As the spring latch meets its locking cutouts at either end of the rail, it will engage. Full length handguard sections should be installed with the spring latches towards the muzzle. Shorter handguard sections (used on rails partially occupied by accessories) should be oriented with their spring latches away from the accessories. (4) Nine rail covers of various lengths are provided with the RAS. They are: Four full length (6.15") sections Two 3.9" (approximately half length) sections 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 1-2. 1-6
DRAFT TC-23-AIMSS Figure 1-11 Installing rail covers l. RAIL COVERS: The rail covers perform two primary functions. RAS. (1) They protect the shooter's hands from direct contact with the metal parts of the (2) They protect the rail surfaces from excess wear and damage. NOTE Rail covers should cover the unused sections of each rail of the RAS at all times. CAUTION Keep unused rail sections covered with full length "11 Rib" handguard sections when not otherwise occupied by accessories. If any accessories are mounted on a rail(s), cover the remaining rail surface(s) with appropriately sized shortened rail covers. 1-6 OPERATION OF THE RAIL ADAPTER SYSTEM a. The odd numbered recoil grooves of each rail of the RAS are sequentially numbered within the recoil grooves themselves. Each number is preceded by letter prefix indicating a specific quadrant rail to provide "addresses" for each recoil groove of the system. The numbers of the top rail have a "T" prefix while those of the bottom rail have a "B" prefix. Additionally, the numbers of the rail to the shooter's left have an "L" prefix while those of the rail to the shooter's right have an "R" prefix. 1-7
DRAFT TC-23-AIMS b. Addresses have three primary uses: (1) They can be used as a memory aid to assist the user in remounting an accessory in the same position. (2) They allow instruction and standardization on precisely where to mount certain accessories. (3) They allow instruction on which accessory addresses may be incompatible with other accessories on the same or adjacent rails. Figure 1-12 Address Markings on Recoil Grooves c. Each RAS also contains three holes within recoil grooves along its length that are threaded l/4" deep with 20 threads per inch (See figure 1-13). This is the standard thread size for a camera tripod Adapter. These are provided for the attachment of standard camera or video accessories. For example, a RAS-equipped M4 carbine with a night vision device mounted may be attached to a standard camera tripod for "hands free" support during long periods of surveillance. d. The installation of the RAS has no adverse effect on the attachment or operation of any current standard accessory. The RAS will not affect the use of the Multiple Integrated Laser Engagement System (MILES), the M7 or M9 bayonets, the M15A2 or M23 blank firing Adapters, the top-carry sling Adapter, or any of the standard slings (all mounting in their standard positions and operated in the standard way). e. With the lower RAS assembly removed (in the same manner as the standard M4 lower handguard is removed), the M203 grenade launcher will mount under the barrel in its standard location. However, it should be secured by the M203 quick attach/detach grenade launcher mount, P/N 95117, which allows the user to quickly install/remove the M203 in the field, once an armorer has installed the mount to the receiver of the M203. f. The M4 Carbine side sling Adapter, if installed, must be positioned so the integral stop, normally positioned towards the muzzle, is to the rear (in accordance with Figure C-2 of Navy SW 370-AE-MM1-010: Unit and Direct Support Maintenance Manual for M203 Grenade 1-8
DRAFT TC-23-AIMSS Launcher). This change in orientation allows the swivel to fold flat towards the muzzle so the M4 side sling Adapter will not interfere with the installation of handguard sections, the forward handgrip, or other accessories that require installation from the muzzle end of the rail. 1-7 MAINTENANCE OF THE RAIL ADAPTER SYSTEM a. CARE AND CLEANING. (1) Clean, inspect, and lubricate the rail surfaces and recoil grooves (slots) of the RAS when the M4 carbine is cleaned and/or when handguard sections or accessories are being installed or repositioned on the rails. (2) Use the general purpose (GP) brush (double-ended toothbrush) from the standard rifle/carbine cleaning kit to clean the RAS. (3) If debris is RAS is observed inside the RAS, remove the lower RAS assembly (or the M203 Grenade Launcher) and detail clean. Thoroughly, but gently, clean the inner surface of the thermal liner to maintain its reflective surface. Do not remove the screw. The screw is secured with lock tighten and must be replaced if removed. CAUTION When the lower RAS is detached from the carbine, protect its polished aluminum thermal liner from being bent or otherwise damaged. Pack it carefully if it is transported in a pouch or rucksack. Do not remove the thermal liner for cleaning. If the thermal liner is removed from the lower RAS, and the lower RAS re-installed on the carbine, the heat protection value of the assembly is diminished. (4) If the RAS is exposed to salt water or corrosive chemicals, remove and thoroughly wash it in warm soapy water and then rinse the upper and lower assemblies in fresh water. Thoroughly clean, dry, and inspect the screw/latch/spring assembly, the latch roll pin, the pins in the rear of the upper RAS assembly, and the spring latches in the handguard sections, after rinsing in water. Lubricate these components as outlined below. (5) Inspect the handguard section contact surfaces for nicks, burrs, or other damage. Inspect accessory rail grabber contact points for similar damage. (6) Use a dry absorbent cloth to wipe away lubricant that inadvertently appears on the surface of polymer handguard sections. b. OPERATOR AND ORGANIZATIONAL MAINTENANCE. (1) Maintenance is limited to inspection and replacements of repair parts. (2) All repair parts can be installed at the operator or unit level. Special tools or equipment are not required for maintaining the RAS. 1-9
DRAFT TC-23-AIMS (3) Inspect and lubricate weekly as a minimum. Daily cleaning and lubrication may be required under some operational conditions. (4) Lightly lubricate the metal components of the RAS assemblies and the spring latches in the handguard sections with CLP (Cleaner, Lubricant, Preservative). Generously lubricate the screw/latch/spring assembly of the upper RAS, especially after exposure to water or high humidity. 1-10