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AT3™ 6.5 Grendel Upper by Faxon

FF-ML 20 Inch 6.5 Grendel Upper – 20 Inch Barrel by Faxon – 15 Inch M-LOK Free Float Handguard


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Lifetime WarrantyOn All AT3 Brand Products

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

This includes AT3 Red Dot Sights, Handguards, Iron 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.

Fast & Free Shipping On orders over $50

You will receive fast, free shipping for all orders over $50

Shipping cost is $7.99 for orders under $50. We ship with UPS or USPS, depending on the item.

Most orders received by 1pm CST ship the same day

You will receive an email with tracking information at the time of shipment. To expedite shipping, we may ship your order from multiple warehouses. Orders placed on weekends, holidays, or after 1pm will ship the following business day.

Our First Match-Grade Upper, Ready for the Discerning Hunter or Marksman – The AT3 20″ 6.5 Grendel Rifle Upper with SPEAR M-LOK Handguard

AT3 Complete Upper assemblies are Built for Accuracy and Reliability – Guaranteed.

  • Quality Where it Counts – premium components like a Faxon Firearms barrel, adjustable gas block, and AT3 Tactical’s handguards and uppers. Don’t settle for “bargain uppers” with unknown components.
  • Guaranteed Reliability– Carefully assembled before shipment, and backed by the AT3 Lifetime Warranty
  • Unbeatable Value – Unbeatable quality in the price range. Save up to 20% off vs purchasing the components separately.

This fully assembled AR-15 complete upper includes:

20″ Faxon Firearms 1:8 416 Stainless Match Grade Barrel

6.5 Grendel Faxon Firearms Barrel

Faxon Firearms makes some of the finest match-grade barrels in the industry, with precision 5R rifling, polished target crowns, and nickel teflon barrel extensions. The straight fluting keeps this heavy barrel as light as can be, without sacrificing repeatable accuracy, and the QPQ finish offers superior corrosion resistance.

Wojtek Weaponry Adjustable Gas Block

The critical component for the best possible feeding and accuracy on your new upper. Wojtek Weaponry’s adjustable gas blocks are easy to adjust to your favorite factory cartridge or handload, and use a clamp-on design to impart better accuracy better than pinned or set-screw gas blocks.

AT3 SPEAR 15″ Free Float M-LOK handguard

15 inch AT3 Tactical SPEAR Handguard

Unique slim and lightweight design with M-LOK attachment points. Rock-solid 6061 aircraft aluminum handguard that withstands the harshest treatment. 5-slot M-LOK-to-Picatinny rail section included

AT3 Tactical Billet Upper Receiver

AT3 Tactical Billet Upper for AR15

Precision machined from 6061-T6 aluminum, this assembled upper is sleek, with extra material around the barrel extension for superior accuracy. It mates perfectly with our SPEAR handguard and feature M4 feedramps for reliable feeding of ammunition.

Faxon Firearms MUZZLOK 3-Port Brake

This 3-Port Brake uses an innovative design with an integrated jam nut, instead of the common crush washer on most AR15 builds. Not only does the design offer significant recoil reduction, but it is also easy to install and remove depending on your specific application.

Optional Upgrades (use the dropdown menu to select):

AT3 6.5 Grendel Black Nitride Bolt Carrier Group

AT3 6.5 Grendel Bolt Carrier Group

(Only $117 – save $10 vs regular price)

AT3 Tactical provides Top-Tier Bolt Carrier Groups with all the uppers we sell. They feature M16-style carriers, MPI inspected bolts made from 9310 steel, and properly staked grade 8 gas key screws.

Your choice of Standard GI or Extended-Latch Charging Handle

(Discounted Pricing – Save $4 vs regular price)

Quality 7075-T6 charging handles – choose between standard latch and extended latch designs.

More info:

This product is built-to-order in our Minnesota facility. Quality takes time – please allow up to 7 days for your order to ship.

All AT3 upper assemblies come with a Lifetime Warranty – if you ever have an issue, let us know, and we’ll make it right. It’s that simple.

Don’t see the options you’re looking for? Let us quote you a custom upper – contact us now.


  • Barrel Length: 20″
  • Total Assembly Length: 26″
  • Gas System: Rifle
  • Barrel Profile: Heavy, Straight Fluted
  • Twist Rate: 1:8
  • Barrel Steel: 416 Stainless Steel
  • Barrel Finish: QPQ Corrosion Resistant (Nitride)
  • Chamber: 6.5 Grendel Type II
  • Muzzle Thread: 5/8×24
  • Barrel Extension: M4
  • Diameter at Gas Block: .750″
  • Gas Block Type: Low-profile
  • Receiver Material: Billet 6061 T6

3 reasons why AT3 Complete Uppers are better than the rest.

1 – Quality Where it Counts

The single most important component of an accurate AR-15 is the barrel. AT3 uppers are built using Ballistic Advantage barrels with a Sub-MOA Accuracy Guarantee.

But the quality doesn’t stop at the barrel. Our AT3 handguard and upper work together to provide superior accuracy, meaning this upper assembly offers quality without compromises.

Many of the “bargain” complete uppers on the market source their parts from the lowest bidder – at the expense of accuracy and reliable function. AT3 is committed to using only top-quality components in our upper assemblies.

2 – Guaranteed Reliability

AT3 complete uppers are assembled with strict quality controls and carefully packaged for delivery to the customer. All AT3 complete uppers offer a Lifetime Warranty – if you ever have an issue, let us know, and we’ll make it right. It’s that simple.

3 – Unbeatable Value

When you buy a complete upper, you’ll save money and parts and assembly vs purchasing the components separately. Our complete uppers are not the cheapest on the market, but they deliver unbeatable quality in the price range. We sell direct to the customer, and cut out the middle-men, to deliver the best value in AR-15 upper assemblies.

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Customer Reviews

Based on 3 reviews
Completed Build - Extra Upper

Excellent fit and finish. Will test fire/break in, as soon as possible.

Thanks for sharing your feedback, JSP. We're glad you're satisfied with your purchase. Cheers!
AT3 FF-ML 20 Inch 6.5 Grendel Complete Upper Range Report
Thanks for sharing your feedback, Jim. We're glad you're satisfied with your purchase. Cheers!
Grendel Upper

Looks great. Have not had opportunity to shoot it yet. Waiting on other components to complete the build.

Thanks for sharing your feedback, Michael. We're glad you're satisfied with your purchase. - AB