Use a strap wrench and carefully tighten the handguard until snug. Adjust the lock ring and handguard until the top rail (marked “T”) is almost aligned with the rail on the upper receiver. Apply blue threadlocker onto the outside barrel nut threads and screw on the quad rail.ġ4. Next, loosen the lock ring and carefully thread the quad rail onto the barrel nut for a couple turns. Tighten the set screws on the gas block securely.ġ3. Apply blue threadlocker onto the gas block set screws and slide the gas block assembly onto the barrel, making sure the gas port in the barrel aligns with the hole in the gas block. Do not partially loosen the barrel nut to achieve alignment – if need be, loosen the nut completely and re-tighten to align correctly.ġ2. The holes should line up at about 35 foot-pounds of torque, and the gas tube should be centered in the barrel nut hole without touching the edges. Without exceeding 60 ft/lbs, tighten the barrel nut until the gas tube hole in the upper receiver and the hole in the barrel nut align perfectly. This three-time torque sequence allows the threads on the upper receiver and barrel nut to mate more completely.ġ1. Torque to 30 ft/lbs one more time and inspect the alignment between the barrel nut hole and the gas tube hole in the upper receiver. Re-torque to 30 ft/lbs, then remove the torque wrench and loosen again.
Remove the torque wrench and loosen the barrel nut with the armorer’s wrench (never loosen with a torque wrench).ġ0. Set your torque wrench to 30 ft/lbs and tighten the barrel nut using your armorer’s wrench. Apply a thin layer of high quality lithium moly grease to the inside threads of the barrel nut, install it over the barrel so that the lock ring faces toward the upper receiver, then hand-tighten the barrel nut.ĩ. Remove the anti-rotation screw from the bottom of the new handguards and unscrew the new barrel nut, removing it from the handguards. Remove the original barrel nut/delta ring assembly with the armorer’s wrench, then clean and inspect the upper receiver threads.Ĩ. Drive the roll pin flush with the gas block.ħ. On a bench block, align the gas tube through-hole (with the large hole facing down) into the new gas block and use a roll pin holder to start the roll pin. Remove the handguard retainer and gas tube.Ħ.
If it sticks, gently tap on it with a soft-faced hammer until it slides off the barrel. Remove the original front sight gas block assembly from the barrel. If the gas block is a clamp-on type, use a hex key to loosen the set screws. Sometimes applying light heat to the area also helps with removal.ĥ. If the pins are difficult to remove, apply penetrating oil, let sit overnight and try again.
If unsure, measure the pin diameter on each side first. If it has tapered pins, drive them out with a cup tip punch from the small side. Tap out the gas tube roll pin with a #2 roll pin punch and inspect the front sight gas block. Clamp the upper receiver into a vise using a vise block and remove the flash hider and crush washer. Separate the upper and lower receivers and remove the bolt carrier group and charging handle.ģ. First, remove the original handguards using a handguard removal tool.Ģ. Make sure you have all the right tools and parts on hand for disassembly and reassembly before starting work.Īs always, before working on any firearm make sure it’s unloaded and safe to handle.ġ. Most standard front sight gas blocks are held onto the barrel by either tapered pins or by clamps. When planning your free-float project, take a close look at the type of gas system currently on your rifle. What do I need to install a free float quad rail handguard? A direct impingement AR-15 can never be truly “free-floated” due to the attachment of the gas block and gas tube, but the addition of a quad rail or other free float style handguard can help with accuracy and also provides a stable and convenient platform for attaching bipods, lights, grips and other accessories. The traditional AR-15 configuration has the sling mount attachment at the base of the front sight gas block, so moderate changes in sling tension can change the point of impact downrange. One of the main benefits to free-floating an AR-15 is an increase in accuracy from reduced variability in the barrel harmonics due to sling tension.