INSTALLATION INSTRUCTIONS FOR VECTR QUADRAIL HANDGUARD

STEP 1 - REMOVAL OF OLD HANDGUARD

  1. Depress delta ring towards receiver and remove upper and lower hanguards.
  2. Remove muzzle brake if so equipped
  3. Remove gas block/ front sight. If it is retained by cross-pins, note that they are tapered and must be driven out by using a punch on the SMALL end of the pins. Support the barrel near the gas block to prevent damage.
  4. Using a properly fitting barrel nut wrench, remove the barrel nut by turning counter-clockwise (looking towards the receiver). Note- MAKE SURE THE UPPER RECEIVER IS FULLY SUPPORTED DURING THIS OPERATION. USE A QUALITY FIXTURE! IF YOU ONLY USE A BARREL VISE , YOU MAY DEFORM THE BARREL ALIGNMENT SLOT IN THE RECEIVER!!!!. Proper tools are readily available from Brownell's or MidwayUSA. USE THEM!!!

STEP 2- INSTALLATION OF NEW HANDGUARD

  1. Install new barrel nut. Tighten by hand until barrel extension is fully seated. Ensure that the alignment pin enters its slot in the receiver.
  2. Use a spanner pin wrench to torque the barrel nut to 35-45 ft/lbs. If you did not purchase one with your handguard, most AR-15 multi-tools include one for the buffer extension tube lock-nut. (see Figs. 1 and 2)
  3. Thread the new handguard onto the barrel nut until it contacts the front of the receiver, then back it off until the top rail is uppermost. Occasionally the dust cover pivot pin is too long and protrudes past the face of the receiver. You can either file a small amount off the end of the pin, or leave a little more gap between the rail and receiver. NOTE- if the rail is almost upright when it contacts the receiver, DO NOT tighten it against the shoulder. There MUST be a small gap between the two, or accuracy will suffer. If you back it off nearly a full turn, the gap will at most be .030".
  4. Use a Picatinny riser or a scope ring to align the top rail with the receiver, straddling the joint and clamping finger-tight. Then tighten the two clamp screws at the bottom of the rail, alternating until both are tight. (max 15 INCH-LBS) (see Fig. 3). Remove riser or scope ring and double check alignment.
  5. Reinstall gas block and brake.

NOTE

For a permanent installation, loctite red can be used sparingly on both the barrel nut- to- handguard threads, and the clamp screws. However, it will be VERY difficult to remove at any point in the future. DO NOT UNDER ANY CIRCUMSTANCES LOCTITE THE BARREL NUT TO THE RECEIVER! Proper torquing is sufficient, and it may be impossible to remove the barrel without damaging the receiver.




Fig 1. Installing barrel nut with DPMS Multi- Tool



Fig 2. Torquing barrel nut. Note how far away torque wrench attaches to multi-tool. In this type of application, reduce torque wrench to 25 ft-lbs



Fig 3. After aligning rail, clamp screws are tightened alternately to 15 INCH lbs (NOT ft-lbs!!!)