How To Install Free Float Quad Rails On AR-15

how to install free float quad rail on ar-15
Alfred Mendoza

Free float-style handguards help increase accuracy by eliminating string tension from the barrel, and quad rail provide a platform for various lights and optics grips. Installing a free float quad rail makes it easier for you to use any firearm. 

Here’s how to install a free-floating quad rail handguard on your AR-15.


1. Make Sure You Have the Right Tools & Parts

It would be best if you had these things before starting: 

  • Vise – It’s a tool for clamping the upper receiver of the quad rail and removing the crush washer.
  • Upper Receiver Vise Block – It holds the upper receiver firmly. It is usually a 2-piece clamshell design.
  • Safety Glasses – Minimum is a Z87 rating is recommended to install a free float quad rail safely. (1)
  • Ball Peen Hammer – We recommend 4-8 ounces.
  • (5/64”) Roll Pin Holder – Use it to gas block roll pin. 
  • Roll Pin Punch – Drive gas block roll pin.
  • Cut Tip Punch – Drive out taper pins.
  • Armorer’s Bench Block – Secures barrel assembly, upper receiver assembly, and charging handle assembly for your quad rail installation.
  • Armorer’s Wrench – It’s for the installation of the barrel nut.
  • ½ Torque Wrench – Tightens barrel nut. 
  • Strap Wrench – Tightens and loosens the parts.
  • Level – Inspects alignment of the upper rail. 
  • Anti-seize Grease – It is used to lubricate bolts for disassembly.

2. Remove Original Handguards & Separate the Receivers

You need to remove the conventional AR-15 handguard. You do this by pulling the ring in the receiver’s direction and gradually eliminating half of the plastic handguard. 

It’s wise to purchase a handguard removal tool if you’re going to do this more than once. It makes the process easier and faster as the ring is under heavy spring pressure.

3. Inspect the Front Sight Gas Block

You need to use a #2 roll pin punch to efficiently tap out the gas tube roll pin of the rail so that you can inspect the front sight gas block. 

If you encounter tapered pints, use a cup tip punch of the small part to drive them out. If you are uncertain, make sure to measure the pin’s diameter per side.

There are times where the pins are tricky to remove, so place penetrating oil if that’s the case, and allow the oil to sit overnight. Another option is heat application, as it speeds up removal.

4. Loosen the Set Screws

For rifle owners who have a clamp-on type of a gas block, you’re going to need a hex key to have the screws loosened. You do this by removing the standard front sight gas block assembly from the rail barrel. 

You can lightly tap on it using a soft-faced hammer if you trouble sliding it off the barrel. After which, pull out the retainer and the gas tube.

loosen screw

5. Align the Gas Tube Through-Hole

The next step is to line up the gas tube through-hole on a bench block. Make sure that the large side is facing down, into your new low-profile gas block. What’s more, start the roll pin using the roll pin holder. Use a gas block to drive the roll pin flush.

Remove the standard delta ring assembly using the armorer’s wrench after doing so, clean and check the threads.

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6. Clean & Inspect the Upper Receiver Threads

At the handguards’ foot, detach the anti-rotation screw, and unscrew the barrel nut to remove it.

Put a papery layer of high-quality lithium moly grease to the threads onto the barrel nut.

To make sure the lock ring faces the receiver, have it installed atop the barrel. Finally, hand tight the barrel nut.

upper receiver threads

7. Set & Re-torque the Wrench

Put the torque barrel nut wrench to 30ft and secure the barrel nut using the armorer’s wrench. Also, make sure to avoid using the torque wrench for loosening.

After which, you need to re-torque to 30ft. Put the torque wrench away and loosen again. For the last time, torque it to 30ft and inspect the line up between the barrel nut and gas tube hole situated in the upper receiver.

In total, you need to do the torque sequences three times to enable the threads of the upper receiver and barrel nut for efficiency.

8. Tighten Barrel Nut & Set Screws

Secure the barrel nut till the gas tube cavity and the barrel nut’s opening are in perfect alignment. When doing this, make sure the wrench does not exceed 60 ft. 

The holes should be aligned at 35 foot-pounds. Meanwhile, the gas tube needs to be centered in the nut hole without the edges touching. 

You can use the bolt carrier to inspect for proper gas tube installation. All you need to do is to insert the bolt carrier group to the upper receiver. 

If you’re having trouble, do not loosen the barrel nut partially to attain ideal alignment, as it won’t help in installing the rail properly.

Tighten Barrel Nuts & Set Screws

9. Thread the Quad Rail & Adjust the Lock Ring

You need to put the blue threadlocker onto the set screws of the gas block. After which, glide the gas block assembly onto the barrel nut to efficiently upgrade your rifle. 

This process ensures the barrel’s gas port is in alignment with the opening in the gas block. Finally, reinforce the set screws on the block properly once you make sure the gas port is aligned before moving to the top rail alignment.

Moreover, you have to adjust the lock ring and the free float handguard until the top rail is close to alignment with the upper receiver’s rail.

10. Reinstall & Reassemble the Devices & Receivers

As for the last step, reinstall the muzzle device with the crush washer and line it properly. The flash hider comes together with the vented ports facing upward and the muzzle brakes generally together with the ports facing the sides.

You need to put a blue threadlocker up on the anti-rotation screw situated at the handguard base. Make sure to hand tighten it.

Reassemble your upper and lower receivers after reinstalling the charging handle and the rail bolt carrier group.

You can place iron sights on a quad rail to assist your aim. However, these sights are typically swapped by telescopic sights for precision applications.

assemble ar 15

Wrapping Up...

While it may be tricky to install a free-floating quad rail handguard to your gun, it’s worth the trouble. A free-floated handguard increases precision and gives you an easy-to-access platform for your lights and grip optics and attaching bipods.

Before installing a free-floating attachment rail, make sure you have all the necessary tools needed for the procedure.

Even if you are a non-handy person, you can install a free float by following the steps above.



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