AT3™ .300 Blackout Medium Profile 16 Inch AR-15 Barrel

SKU: AT3-300-16

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AT3™ Upper Receiver and SPEAR Handguard Combo

AT3™ AR 15 Upper Receiver and SPEAR Handguard Combo - Black, 15 inch


16 Inch .300 Blackout Barrel by AT3 Tactical

A 16 inch .300 Blackout barrel makes swapping to a heavier hitting cartridge in your favorite rifle simple. This 4150 CMV barrel features a medium profile, providing plenty of support for mounting a suppressor, without feeling cumbersome in the field. It also gets a black nitride finish for corrosion resistance, and has M4 feed ramps for optimal reliability.

This barrel uses a .750″ diameter gas block, plus a Pistol length gas tube, both of which you can snag here at a lower, bundled cost. If you’re looking to start fresh with a complete upper assembly, check out our selection of upper and handguard combos! For this barrel, we’d recommend a handguard at least 12 to 15 inches long for shooter comfort, and space for accessories.


  • Length: 16 Inches
  • Material: 4150 Chrome Moly Vanadium
  • Profile: Medium
  • Finish: Black Nitride
  • Gas System Length: Pistol
  • Gas Block Journal: .750″
  • Twist Rate: 1:7 inches
  • Muzzle: 5/8×24 Threaded
  • Barrel Extension: M4 Feed ramps
  • Weight: 29 oz.

Where are these barrels made?

AT3 has partnered with Kinetic Manufacturing, a trusted OEM manufacturer for the firearm industry to produce these barrels. We have a philosophy that great parts for the AR don’t have to break the bank, and these barrels are no exception. Our lifetime warranty on these barrels applies to any defects due to workmanship. In the unlikely event you run into an issue, we will take care of you.


Caliber.300 Blackout
Barrel Length16 inches
Barrel Twist Rate1:7 inches
Barrel Material4150 CMV
Muzzle Threads5/8/2024
Barrel FinishBlack Nitride
Gas Block Size.750″ Gas Block
Barrel ProfileMedium
Barrel Gas SystemPistol
Gas Block Journal Length1.9 inches
Barrel ExtensionM4
Weight29 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.

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 1 review
Michael Russell
Great barrel

I used the barrel with at3 upper receiver and bcg. The first time out sighting it I shot 5 groups of five at 50 yards using AAC amo. I stcked each group with only one flyer. Performed perfectly now we will se on the long game if it holds up.

Thanks for the review! We're glad you liked it!