$336.61
Availability: In Stock
The CMMG 16.1" 5.7x28mm barrel and bolt carrier group kit gives you the core components to build a compact AR pistol or short-barreled rifle in the modern 5.7x28mm cartridge. This kit pairs CMMG's 16.1-inch barrel with a matched bolt carrier group engineered around the company's proprietary Radial Delayed Blowback system—a design that sets it apart from the lighter recoil impulse and reliability you'd expect from a purpose-built 5.7 AR platform.
What makes Radial Delayed Blowback relevant to you: compared to straight blowback systems, it manages recoil signature and bolt carrier weight differently, while retaining functional features like last-round bolt hold open. If you're building a compact tactical rifle, a truck gun, or an AR pistol chambered in 5.7x28mm, this kit handles the heavy lifting. The barrel is ready to drop into a standard Mk4/mil-spec AR15 upper receiver; the BCG works with either a CMMG Mk57 lower receiver or a standard AR15-pattern lower when paired with CMMG 5.7 conversion magazines.
This is a barrel-and-bolt package, not a complete upper or firearm, so you'll supply the upper receiver, lower receiver, and furniture. 5.7x28mm ammo is compact, mild-shooting, and increasingly available—ideal if you want sub-rifle ballistics in a configurable platform.
| Barrel Length | 16.1 inches |
| Caliber | 5.7x28mm |
| Operating System | CMMG Radial Delayed Blowback |
| Finish | Black |
| Compatible Upper Receiver | Mk4/mil-spec AR15 |
| Compatible Lower Receiver | CMMG Mk57 or Mk4/AR15 mil-spec (with CMMG 5.7 conversion magazines) |
The kit is compatible with a CMMG Mk57 lower receiver. It also works with a standard Mk4/AR15 mil-spec lower receiver when you use CMMG 5.7 AR conversion magazines.
This kit contains the barrel and bolt carrier group only. You will need to source a Mk4/mil-spec AR15 upper receiver to complete the upper assembly.
CMMG's Radial Delayed Blowback system manages recoil impulse and bolt carrier weight differently than a direct blowback design, resulting in less felt recoil while maintaining features like last-round bolt hold open.
5.7x28mm is a compact, low-recoil cartridge that delivers sub-rifle ballistics. It's commonly used in AR pistols and short-barreled rifles for tactical applications, training, and shooters who prefer mild recoil with a standard AR-platform ergonomic.
SKU: 115831666 • Weight: 2.69oz
Availability: In Stock
The CMMG 16.1" 5.7x28mm barrel and bolt carrier group kit gives you the core components to build a compact AR pistol or short-barreled rifle in the modern 5.7x28mm cartridge. This kit pairs CMMG's 16.1-inch barrel with a matched bolt carrier group engineered around the company's proprietary Radial Delayed Blowback system—a design that sets it apart from the lighter recoil impulse and reliability you'd expect from a purpose-built 5.7 AR platform.
What makes Radial Delayed Blowback relevant to you: compared to straight blowback systems, it manages recoil signature and bolt carrier weight differently, while retaining functional features like last-round bolt hold open. If you're building a compact tactical rifle, a truck gun, or an AR pistol chambered in 5.7x28mm, this kit handles the heavy lifting. The barrel is ready to drop into a standard Mk4/mil-spec AR15 upper receiver; the BCG works with either a CMMG Mk57 lower receiver or a standard AR15-pattern lower when paired with CMMG 5.7 conversion magazines.
This is a barrel-and-bolt package, not a complete upper or firearm, so you'll supply the upper receiver, lower receiver, and furniture. 5.7x28mm ammo is compact, mild-shooting, and increasingly available—ideal if you want sub-rifle ballistics in a configurable platform.
| Barrel Length | 16.1 inches |
| Caliber | 5.7x28mm |
| Operating System | CMMG Radial Delayed Blowback |
| Finish | Black |
| Compatible Upper Receiver | Mk4/mil-spec AR15 |
| Compatible Lower Receiver | CMMG Mk57 or Mk4/AR15 mil-spec (with CMMG 5.7 conversion magazines) |
The kit is compatible with a CMMG Mk57 lower receiver. It also works with a standard Mk4/AR15 mil-spec lower receiver when you use CMMG 5.7 AR conversion magazines.
This kit contains the barrel and bolt carrier group only. You will need to source a Mk4/mil-spec AR15 upper receiver to complete the upper assembly.
CMMG's Radial Delayed Blowback system manages recoil impulse and bolt carrier weight differently than a direct blowback design, resulting in less felt recoil while maintaining features like last-round bolt hold open.
5.7x28mm is a compact, low-recoil cartridge that delivers sub-rifle ballistics. It's commonly used in AR pistols and short-barreled rifles for tactical applications, training, and shooters who prefer mild recoil with a standard AR-platform ergonomic.
SKU: 115831666 • Weight: 2.69oz