CMMG 6mm ARC 20 Inch AR 15 Barrel – 416R Stainless Steel – Rifle Length – Matte Stainless


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AT3™ Low Profile Steel Gas Block + Gas Tube + Roll Pin Combo

AT3™ Low Profile Steel Gas Block + Gas Tube Combo - .750" Gas Block, Rifle Tube


Precision Rifle Ready – Stainless 6mm ARC Barrel

Constructed from stainless steel for the most accurate rifling you can get, this 6mm ARC barrel from CMMG delivers on everything you’d want from a precision caliber conversion.  The barrel features a tapered profile to make handling easier, while retaining enough mass for repeatable accuracy at long range.  The rifle-length gas system also keeps recoil mild, and a full 20 inch length keeps rounds at high velocity for extended range use.

What is 6mm ARC?

This new cartridge from Hornady lives up the acronym – the Advanced Rifle Cartridge.  6mm ARC uses a heavier bullet for better ballistics and less wind deflection, and is capable of reaching out to 1000 yards or more.  In addition, the case shares the same case head as 6.5 Grendel Type II, allowing you to use the same type of bolt carrier group.  Magazines for 6.5 Grendel also work perfectly for a complete, reliable caliber conversion.


  • Length: 20″
  • Material: 416R Stainless Steel
  • Profile: MT
  • Finish: Matte Stainless Steel
  • Gas System Length: Rifle Length
  • Gas Block Journal: .750″
  • Twist Rate: 1:7.5 inches
  • Muzzle: 5/8×24 Threaded
  • Weight: 36 oz.


Caliber6mm ARC
Barrel Length20 inches
Barrel Twist Rate1:7.5 inches
Barrel Material416 Stainless
Muzzle Threads5/8/2024
Barrel FinishMatte Stainless
Gas Block Size.750″ Gas Block
Barrel ProfileMedium
Barrel Gas SystemRifle
Gas Block Journal Length1.1 inches
Barrel ExtensionM4
Weight36 ounces

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.

CMMG Warranty

Seller warrants to Buyer that for a period of 6 months from the Delivery Date, all Goods will be:

  • Free from any defects in workmanship, material, and design
  • Conform to applicable specifications[, drawings, designs, samples and other requirements specified by Buyer]
  • Fit for their intended purpose and operate as intended
  • Merchantable
  • Free and clear of all liens, security interests or other encumbrances
  • Not infringe or misappropriate any third party’s patent or other intellectual property rights.

Inspection and Rejection of Nonconforming Goods

The Buyer has the right to inspect the Goods for a period of thirty (30) days after the Delivery Date. Buyer, at its sole option, may inspect all or a sample of the Goods and may reject all or any portion of the Goods if it determines the Goods are non-conforming or defective.

If Buyer rejects any portion of the Goods, Buyer has the right, effective upon written notice to Seller, to:

  • Rescind the Order in its entirety
  • Accept the Goods at a reasonably reduced price
  • Reject the Goods and require replacement of the rejected Goods.


If Buyer requires replacement of the Goods, Seller shall, at its expense, promptly/within 30 days replace the nonconforming Goods and pay for all related expenses, including, but not limited to, transportation charges for the return of the defective goods and the delivery of replacement Goods.

If Seller fails to timely deliver replacement Goods, Buyer may replace them with goods from a third party and charge Seller the cost thereof and terminate this Order for cause pursuant to Section 20.

Any inspection or other action by Buyer under this Section shall not reduce or otherwise affect Seller’s obligations under the Order, and Buyer shall have the right to conduct further inspections after Seller has carried out its remedial actions.

Disclaimer: Manufacturer’s warranty is subject to change without prior notice.