AT3™ AR 15 Upper Receiver and Pro Quad Rail Handguard Combo

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AT3™ AR-15 Bolt Carrier Group -  5.56 NATO/.300 Blackout - Black Nitride

AT3™ AR-15 Bolt Carrier Group – 5.56 NATO/.300 Blackout – Black Nitride


Upgrade or Start Your Next Build with our Newest Billet Upper and Pro Quad Rail Handguard Combo

The AT3™ Pro Quad Rail, like the SPEAR,  is designed for use with our matching Billet Upper Receiver as well as the majority of mil-spec AR-15 uppers on the market. The quad rail is the gold standard of a secure accessory mounting and that’s what we offer with this AT3 Pro Quad Rail and Billet Upper Combo.  It uses the same simple installation as our SPEAR M-LOK handguard, lightened up and improved for maximum comfort, and works perfectly with Mil-spec AR-15 builds to match the sleek contours.

Improved Design and Easy Installation

The Pro Series Rail comes in 7″, 9″, 12.5″, and 15″ inch lengths, making it ideal for upgrading existing guns or starting fresh with specialized AR15 builds. If you’re planning a build without a Front Sight Base, make sure you pick up a Low Profile Gas Block with the handguard.

AT3™ Upper Receiver and Pro Quad Rail Handguard Combo

Solid and Secure Mounting

  • This rail is lightened down all four sides of Picatinny Rail, making it lightweight while still remaining solid for all your favorite accessories
  • 5 Integrated non-rotating QD Sockets for a variety of sling configurations
  • Durable 6061 aircraft aluminum alloy construction – designed to take a beating
  • Picatinny top rail perfectly aligns with AR-15 flat-top upper receivers, both forged and our AT3 Billet Upper
  • Handguard uses screws to clamp around the barrel nut, with anti-rotation tabs and anti-slip screws that ensure a rock-solid lockup

Simple Installation

  • Installs easily, just like our SPEAR M-LOK rail – you’ll only need a few simple tools to get the rail installed. Click here to view our instructions.
  • Perfect for assembling a new build or upgrading an existing rifle – it’s compatible with most mil-spec upper receivers on the market
  • Once you’ve got it installed, you’ll have plenty of room for any Picatinny rail accessories like lights, foregrips, lasers, or bipods
  • Seriously, it’s easy. Check out our video below for a guide on the complete installation.

Exceptional Fit and Finish

  • Durable matte-black anodized finish resists scratches and provides an attractive surface that matches the rest of your build
  • Vented rails on all 4 sides reduce weight and help dissipate heat from shooting
  • Scalloped rails and clean lines for a unique look that flows into the AT3 Billet Upper
  • Proudly made in the USA
  • Backed by the AT3 Lifetime Warranty

More Information

Full kit – includes Billet upper receiver, Quad Rail handguard with all mounting hardware, barrel nut, and barrel nut wrench.

If You’re Keeping Your Front Sight Base:

Use the appropriate length rail for your gas system:

  • Carbine Length – 7″ Pro Quad Rail
  • Midlength – 9″ Pro Quad Rail
  • Rifle Length – 12.5″ Pro Quad Rail

Included in the box:

  • AT3 Billet Upper Receiver
  • AT3 Pro Handguard
  • 7075 T6 Aluminum Barrel Nut
  • Mounting Hardware with Allen Wrenches
  • Barrel Nut Wrench


  • Rifle Type: AR-15 (If you have a .308 AR variant, check out our AR-10 / .308 page)
  • Handguard Material: 6061-T6 Aluminum
  • Standard Finish: Hardcoat Anodized Black
  • Cerakote Finishes
    • Flat Dark Earth: H-267 Magpul® Flat Dark Earth
    • OD Green: H-232 Magpul® OD Green
    • Gray: H-188 Magpul® Stealth Grey
    • Pink: H-224 SIG™ Pink
    • Burnt Bronze: H-148 Burnt Bronze
    • Tungsten: H-237 Tungsten
    • Titanium: H-170 Titanium
  • Handguard inside diameter: 1.35”
  • Barrel Nut Material: 7075-T6 Aluminum
  • Barrel nut inside diameter: 1.02” (compatible with barrels up to 1” diameter)
  • Weight
    • 7″ Handguard – 9 oz
    • 9″ Handguard – 12 oz
    • 12″ Handguard – 15 oz
    • 15″ Handguard – 1 lbs 2oz
    • Hardware (Barrel Nut and Screws) 1.6 oz.
  • Actual Handguard Length
    • 7″ – 7″
    • 9″ – 9″
    • 12.5″ – 12.5″
    • 15″ – 15.0″

What tools and additional parts are required?

For parts – most setups will require a low profile gas block.

For tools – we recommend:

  • A vise and non-marring vise block for holding the upper
  • A torque wrench and breaker bar to assure you stay in the AR-15 barrel nut torque range while timing the barrel nut (30-60 ft lbs)
  • Blue Loctite for the mounting screws

Note: This product will not work with non-milspec upper receivers like the Bushmaster Carbon due to the non-standard barrel threads, and it is not compatible with most piston kits as they won’t fit under the handguard. Additionally, this rail will not work with gas blocks that are irregularly shaped or exceed 1.3 inches in height or width.

Products available on this page:

Have Questions About this Product?

The AT3 Tactical store has a 90 day no-hassle return policy for products in good condition. You can view the full details of our return policy here.

If you encounter an issue or defect with a product after 90 days of your purchase, you can refer to the manufacturer for a warranty claim. Their policies are below.

AT3 Lifetime Warranty Logo

All AT3 Tactical Brand Products carry a lifetime warranty against manufacturer’s defects.

This includes AT3 Red Dot SightsHandguardsIron Sights, and any other product that carries the “AT3 Tactical” or “AT3™” name. For other brands (ex. Magpul or Troy), please refer to the manufacturer’s warranty policy.

In the event that your AT3™ product becomes unusable, we will repair or replace the product at no charge to you.

If we cannot repair your product, we will replace it with a product in perfect working order of equal or better physical condition. The warranty is fully transferable, but we may require information about the original purchase to validate the authenticity of the product.

If your product is in need of warranty service, please contact AT3 Tactical to start the process

Our contact info is available here. To expedite processing, please provide your order information and description of the defect.

Please note: The AT3 Lifetime Warranty does not cover loss, theft, intentional damage or cosmetic damage that doesn’t affect the performance of the product.

Customer Reviews

Based on 16 reviews
Ryan Holifield
Great Upper Combos

I purchased two upper combos they look great and feel very sturdy. One thing I’d add is blue loctite to the kit, and as well as in the instructions. All in all great. I’d buy more. So send me so more!

Thanks for sharing your feedback! We're glad you're satisfied with your purchase.

Nicholas Fussell
AT3 UR & 1913 rail handguard. Again, excellent quality. Along with function. Light & durable.

See above.
Used for long desired "lmg" build. See attached file.

Thanks for sharing your feedback! We're glad you're satisfied with your purchase.

Greg Bhullar

Great quality product for the best price, fitting and finish is excellent.

Thanks for sharing your feedback! We're glad you're satisfied with your purchase.

Blake D.

Looked around for a while looking for a rail and upper that I liked. Even bought some stuff. I actually gave away the stripped receiver I bought somewhere else and I’m ordering another one from AT3 with the mlok rail so I can have one with each.

Thanks for sharing your feedback! We're glad you're satisfied with your purchase. Cheers!

Carlos Alfaro
15” upper and Handguard

I loved your upper and handguard