Installing A Free Floating Quad Rail

  1. Installing A Free Floating Quad Rail Barrel Nut
  2. Free Floating Anxiety
  3. Installing A Free Floating Quad Rail Fence

2 Piece Drop-In vs Free Float? Quad rail handguards generally come in one of two form factors: 2 Piece Drop-In or Free Float. The decision to buy one or the other depends on 1) how much effort you want to put into installing the quad rail and 2) how ultra precise you want your rifle to be. A 2 Piece Drop-In Quad Rail, as the name implies, comes in two pieces and screws together into place. AT3™ Pro Quad Rails – Free Float AR15 Handguards – 4 Lengths Available. The New and Improved Pro Quad Rail - Lightweight, Rigid, and Easier to Install The quad rail is still the gold standard of secure accessory mounting, but they're in desperate. At minimum, installation of a free float quad rail handguard requires a vise, an upper receiver vise block, a hammer and punch set, and a AR-15 armorer tool. Please see our AR-15 Free Float Quad Rail Installation Guide for more details. 15' Lo-Pro Slope Nose (LPSN15) Free Float Quad Rail. SAVE $10.00 when you purchase the LPSN15 and a Direct Thread accessory. Simply add both items to your cart. Eligible components that are compatible with the LPSN15: LPSN15/LPSN13 Small Rail. Mini Hand Stop - Direct Thread.

Floating

2 Piece Drop-In vs Free Float?

Quad rail handguards generally come in one of two form factors: 2 Piece Drop-In or Free Float. The decision to buy one or the other depends on 1) how much effort you want to put into installing the quad rail and 2) how ultra precise you want your rifle to be.


A 2 Piece Drop-In Quad Rail, as the name implies, comes in two pieces and screws together into place between the AR-15 receiver and front sight/gas block. The tapered end fits into the delta ring, which holds the quad rail in place against the end cap on the rear of the front sight. For more details, please see our AR-15 2 Piece Drop-In Quad Rail Installation Guide.
The key selling points of a 2 Piece Drop-In Quad Rail are:
- They are typically less expensive
- They are easier to install and require no special tools or gunsmithing experience.
A 2 Piece Drop-In Quad Rail can be installed by anyone in a few minutes. It requires no special tools, though we do recommend using an AR-15 Handguard Removal Tool.


A Free Float Quad Rail differs from a 2 Piece Drop-In Quad Rail in that it attaches directly to the AR-15 lower receiver and does not come into contact with the front sight, and by extension, the barrel. The idea behind this is that a 2 Piece Drop-In Quad Rail, being in constant contact with the barrel, will exert a tiny amount of force on the barrel and will ever so slightly impact the precision of the rifle.
The key selling point of a Free Float Quad Rail is:
- Free float quad rails do not come in contact with the barrel and thus do not impact the precision of the rifle.
The main drawback of a free float quad rail is that installation requires special tools and a more gunsmithing expertise. At minimum, installation of a free float quad rail handguard requires a vise, an upper receiver vise block, a hammer and punch set, and a AR-15 armorer tool. Please see our AR-15 Free Float Quad Rail Installation Guide for more details. If you do not have experience installing a free float quad rail, we highly recommend consulting an experienced gunsmith.

To view our selection of AR-15 quad rail handguards, you can follow these links:
Monstrum Tactical 2 Piece Drop-In Quad Rail Handguards

Why install a free float handguard?

Installing A Free Floating Quad Rail Barrel Nut

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. 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. 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.

Free Floating Anxiety

What do I need to install a free float quad rail handguard?

When planning your free-float project, take a close look at the type of gas system currently on your rifle. Most standard front sight gas blocks are held onto the barrel by either tapered pins or by clamps. Make sure you have all the right tools and parts on hand for disassembly and reassembly before starting work.

Step-by-Step Installation

As always, before working on any firearm make sure it’s unloaded and safe to handle.

1. First, remove the original handguards using a handguard removal tool.

2. Separate the upper and lower receivers and remove the bolt carrier group and charging handle.

3. Clamp the upper receiver into a vise using a vise block and remove the flash hider and crush washer. The crush washer will not be reused.

4. Tap out the gas tube roll pin with a #2 roll pin punch and inspect the front sight gas block. If it has tapered pins, drive them out with a cup tip punch from the small side. If unsure, measure the pin diameter on each side first. If the pins are difficult to remove, apply penetrating oil, let sit overnight and try again. Sometimes applying light heat to the area also helps with removal.

5. If the gas block is a clamp-on type, use a hex key to loosen the set screws. Remove the original front sight gas block assembly from the barrel. If it sticks, gently tap on it with a soft-faced hammer until it slides off the barrel. Remove the handguard retainer and gas tube.

6. 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. Drive the roll pin flush with the gas block.

7. Remove the original barrel nut/delta ring assembly with the armorer’s wrench, then clean and inspect the upper receiver threads.

8. Remove the anti-rotation screw from the bottom of the new handguards and unscrew the new barrel nut, removing it from the handguards. 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.

9. Set your torque wrench to 30 ft/lbs and tighten the barrel nut using your armorer’s wrench. Remove the torque wrench and loosen the barrel nut with the armorer’s wrench (never loosen with a torque wrench).

Installing A Free Floating Quad Rail

10. Re-torque to 30 ft/lbs, then remove the torque wrench and loosen again. 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. This three-time torque sequence allows the threads on the upper receiver and barrel nut to mate more completely.

11. 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. 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. Do not partially loosen the barrel nut to achieve alignment – if need be, loosen the nut completely and re-tighten to align correctly.

12. 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. Tighten the set screws on the gas block securely.

Installing A Free Floating Quad Rail Fence

13. Next, loosen the lock ring and carefully thread the quad rail onto the barrel nut for a couple turns. Apply blue threadlocker onto the outside barrel nut threads and screw on the quad rail.

14. Adjust the lock ring and handguard until the top rail (marked “T”) is almost aligned with the rail on the upper receiver. Use a strap wrench and carefully tighten the handguard until snug. Be careful not to over-tighten; if too much torque is applied, it can misalign the barrel nut and gas tube underneath.

15. You can check for proper gas tube installation using the bolt carrier at this time: insert the bolt carrier group (without the charging handle) into the upper receiver and slowly slide it forward, checking to make sure the carrier gas key doesn’t bind on the gas tube.

16. Take a reading with your level across the top of the upper receiver and compare it with the level of the quad rail. Adjust the quad rail rotation until it matches the level of the upper receiver.

17. Reinstall the muzzle device with a new crush washer and align it correctly (flash hiders generally with the vented ports facing upward; muzzle brakes generally with the ports facing sideways).

18. Then apply blue threadlocker onto the anti-rotation screw on the bottom of the handguard, install it, and tighten until snug.

19. Reinstall the charging handle and bolt carrier group, then reassemble the upper and lower receivers and you’re done!