How to Install a YHM Freefloat Rail

The free-float rail forearm from Yankee Hill Machine (YHM) installs on AR15-style rifles to add a military-spec Picatinny rail for optics and other accessories and mounting points for a sling. Fabricated of aircraft grade aluminum, the rail incorporates anti-rotation screws for stability under conditions of barrel heat and strenuous use. The YHM free-float rails are available in four lengths ranging from the 4.150-inch Mini to the 9.675-inch Specter length.

Things You'll Need

  • AR15 barrel wrench
  • 1/8-inch pin punch
  • Hammer
  • Flat blade screwdriver
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Instructions

    • 1

      Make sure the rifle is unloaded and keep it pointed in a safe direction.

    • 2

      Take off the factory handguard. Hold the rifle with the muzzle pointing up. Pull down on the delta ring at the base of the handguard, compressing the spring action until the mounting tabs on each handguard half clear the delta ring. Spread the two halves of the handguard and pull them free of the front mount.

    • 3

      Unscrew the muzzle brake or flash hider from the muzzle.

    • 4

      Remove the two tapered dowel pins from the front sight base. Use a small hammer and 1/8-inch pin punch to tap the pins out from the left side of the front sight base to the right.

    • 5

      Remove the front sight assembly and the attached gas tube from the barrel.

    • 6

      Loosen and remove the combination barrel nut/delta ring with an AR15 barrel nut wrench.

    • 7

      Clean the barrel nut threads. Slip the supplied new barrel nut over the end of the barrel and slide it down to the receiver. Tighten by hand.

    • 8

      Tighten the barrel nut further with the AR15 barrel nut wrench until the next gas tube hole in the barrel nut aligns with the gas port in the receiver.

    • 9

      Screw the jamb nut on the barrel nut until it is even with the end of the barrel nut facing the receiver, then back it off 1-1/2 turns.

    • 10

      Slip the free-float rail forearm over the end of the barrel and slide it down to the barrel nut. Screw the forearm onto the barrel nut until it contacts with the jamb nut. Make sure the holes for the anti-rotation screws are positioned at 3 o'clock and 9 o'clock and the sling mounting holes are closest to the muzzle.

    • 11

      Hold the forearm and tighten the jamb nut against it using the YHM forearm wrench or a flat blade screwdriver.

    • 12

      Install the two anti-rotation screws and tighten.

    • 13

      Reinstall the front sight, routing the gas tube through the opening in the free-float rail forearm, the hole in the barrel nut and into the receiver gas port.

    • 14

      Tap in the two tapered pins securing the front sight base.

    • 15

      Screw the muzzle brake or flash hider on the end of the barrel.