Free Shipping & Free Returns*

FREE SHIPPING on Over 250,000 Products

Enjoy free shipping during the holidays! Shop now and get Free Value Shipping on most orders over $49 to the contiguous 48 states, DC and to all U.S. Military APO/FPO/DPO addresses.

Enjoy Our Extended FREE RETURNS

We want to ensure that making a return is as easy as possible! With our Hassle-Free, Extended Holiday Returns, eligible orders placed from November 12, 2025 on will benefit from an extended return deadline (January 13, 2026 or 30 days after receipt of your order - whichever is later). We'll even cover the cost of return shipping. Learn more about our Return Policy.

Shopping Cart
Questions & Answers
Finish: Bead Blasted Fabric/Material: 416 Stainless Steel Caliber: 5.56x45mm NATO Barrel Length: 16.1 inBarrel Profile: Heavy Taper Gas System Length: Mid Length Gas Block Journal Size-Diameter: .936 inThreads per Inch: 1/2x28 Barrel Twist Rate: 1-7 Flutes: Yes Gun Model: AR-15 Included Accessories: Standard Gun Type: Rifle

Code: 2CM-ATB-556NTAS-55DFD0C-55D910A

MPN: 55D910A

UPC: 815835016207

Product No Longer Available

Product Info for CMMG, Inc 5.56x45mm NATO Mk4 Barrel Sub-Assembly

CMMG, Inc 5.56x45mm NATO Mk4 Barrel Sub-Assembly is perfect for building your custom AR15 upper group. Comes with properly installed M4 barrel extension. All barrel sub-assemblies are properly headspaced.image

Package Contents:

  • CMMG, Inc 5.56x45mm NATO Mk4 Barrel Sub-Assembly

Gunsmithing Tools & Accessories

1–17 / 17
Previous
Next

Gun Parts and Accessories

1–29 / 29
Previous
Next

Gun Barrels

1–12 / 12

Magazine and Accessories

1–22 / 22
Previous
Next

Gun Triggers

1–14 / 14
Previous
Next

Gun Sights

1–20 / 20
Previous
Next

Gun Stocks

1–19 / 19
Previous
Next

Mounts, Rings and Accessories

1–17 / 17
Previous
Next

Related Products to CMMG, Inc 5.56x45mm NATO Mk4 Barrel Sub-Assembly

CMMG, Inc 5.56x45mm NATO Mk4 Barrel Sub-Assembly Unavailable & Discontinued Models

List of Unorderable Models

  • CMMG Barrel Sub-Assm, 16.1in, Heavy Taper Profile, Bead Blasted, 1-7 Twist, 5.56mm, 1/2x28 Thread, Mid Length, .936 Gas Journal 55D910A , MPN: 55D910A , UPC: 815835016207 , Code: 2CM-ATB-556NTAS-55DFD0C-55D910A
  • CMMG Barrel Sub-Assm, 20in, Light Taper Profile, Salt Bath Nitride, 1-7 Twist, 5.56mm, 1/2-28 Thread, Rifle Length, .750 Gas Journal 55DD10C , MPN: 55DD10C , UPC: 815835018171 , Code: 2CM-ATB-556NTAS-55DFD0C-55DD10C
  • Kinetic MREX AR MLOK 11.6, CMMG Barrel 16.1in 4140CM 5.56 MT, CMMG Mid Gas Tube w/Pin, CMMG Gas Block Low Pro .750in BLACK , MPN: ARP5-010-KIT9 , Code: 2CM-ATB-556NTAS-55DFD0C-ARP5-010-KIT9
  • Kinetic MREX AR MLOK 11.6, CMMG Barrel 16.1in 4140CM 5.56 HT, CMMG Mid Gas Tube w/Pin, CMMG Gas Block Low Pro .750in BLACK , MPN: ARP5-010-KIT10 , Code: 2CM-ATB-556NTAS-55DFD0C-ARP5-010-KIT10
  • Kinetic MREX AR MLOK 11.6, CMMG Barrel 16.1in 416SS 5.56 MT, CMMG Mid Gas Tube w/Pin, CMMG Gas Block Low Pro .750in BLACK , MPN: ARP5-010-KIT11 , Code: 2CM-ATB-556NTAS-55DFD0C-ARP5-010-KIT11
  • Kinetic MREX AR MLOK 11.6, CMMG Barrel 16.1in 416SS 5.56 HT, CMMG Mid Gas Tube w/Pin, CMMG Gas Block Low Pro .750in BLACK , MPN: ARP5-010-KIT12 , Code: 2CM-ATB-556NTAS-55DFD0C-ARP5-010-KIT12
Compare (0)