Brownells194200181
Brownells Brn-4 5.56X45 13.7'' Medium Chrome Lined Barrel, Phosphate$339.99
Availability: In Stock
The Brownells BRN-4/M27 5.56x45 barrel is a 16.5-inch performance upgrade purpose-built for the BRN-4 platform and compatible HK-pattern receivers. Manufactured by Faxon, this chrome-lined, manganese phosphate-finished barrel delivers the M27-inspired configuration shooters have been asking for, combining a robust 1-7 twist bore with a forward-mounted bayonet lug for tactical or historical accuracy builds. Whether you're upgrading an existing upper or building from scratch, this barrel brings genuine military-heritage features to a modern platform.
Built from 4150 chrome moly steel with a precision-buttoned bore, the barrel chamber is chrome-lined for durability and corrosion resistance—a practical choice for shooters who run hard-use ammunition or train in demanding conditions. The ½-28 threaded muzzle accepts standard A2 flash hiders or any common AR15-pattern muzzle device, giving you flexibility in your setup. The M4 feed ramps accommodate a full range of .223 and 5.56 ammunition, so you're not locked into one type of round.
The forward bayonet lug is a distinctive feature: it installs the same way as the gas block, with a simple coil pin driven from the side, creating an extremely robust mount. This design makes the bayonet attachment one of the most solid options available. Keep in mind you'll need a BRN-4 16-inch gas block to run this barrel properly, and the lug installs after the gas block is mounted.
Compatible with Brownells BRN-4 upper receiver groups, as well as HK, 416, MR556, and MR223 platforms, this barrel opens up options if you're working across multiple rifle platforms or planning a modular build.
| Platform | BRN-4 / HK-pattern |
| Caliber | 5.56x45 NATO |
| Barrel Length | 16.5 inches |
| Material | 4150 Chrome Moly Steel |
| Finish | Manganese Phosphate |
| Bore Profile | Medium |
| Twist Rate | 1-7 (Buttoned) |
| Chamber | 5.56x45 NATO (Chrome-Lined) |
| Muzzle Threads | ½-28 |
| Feed Ramps | M4 |
| Front Feature | Forward-Mounted Bayonet Lug |
| Manufacturer | Faxon (for Brownells) |
Yes. While designed for the Brownells BRN-4 platform, this barrel is also compatible with HK, 416, MR556, and MR223 receivers, making it a versatile choice if you're building across multiple platforms.
You'll need a Brownells BRN-4 16-inch gas block. The bayonet lug installs after the gas block using the same coil-pin method, so proper gas block fitment is essential.
Yes. The barrel features ½-28 threads, which accept the standard A2 flash hider found on the M27, as well as any common AR15-pattern muzzle device.
The M4 feed ramps and chrome-lined chamber are designed to work with a wide range of .223 and 5.56 NATO ammunition, giving you flexibility in what you run.
SKU: 167527886 • Weight: 2.25oz
Availability: In Stock
The Brownells BRN-4/M27 5.56x45 barrel is a 16.5-inch performance upgrade purpose-built for the BRN-4 platform and compatible HK-pattern receivers. Manufactured by Faxon, this chrome-lined, manganese phosphate-finished barrel delivers the M27-inspired configuration shooters have been asking for, combining a robust 1-7 twist bore with a forward-mounted bayonet lug for tactical or historical accuracy builds. Whether you're upgrading an existing upper or building from scratch, this barrel brings genuine military-heritage features to a modern platform.
Built from 4150 chrome moly steel with a precision-buttoned bore, the barrel chamber is chrome-lined for durability and corrosion resistance—a practical choice for shooters who run hard-use ammunition or train in demanding conditions. The ½-28 threaded muzzle accepts standard A2 flash hiders or any common AR15-pattern muzzle device, giving you flexibility in your setup. The M4 feed ramps accommodate a full range of .223 and 5.56 ammunition, so you're not locked into one type of round.
The forward bayonet lug is a distinctive feature: it installs the same way as the gas block, with a simple coil pin driven from the side, creating an extremely robust mount. This design makes the bayonet attachment one of the most solid options available. Keep in mind you'll need a BRN-4 16-inch gas block to run this barrel properly, and the lug installs after the gas block is mounted.
Compatible with Brownells BRN-4 upper receiver groups, as well as HK, 416, MR556, and MR223 platforms, this barrel opens up options if you're working across multiple rifle platforms or planning a modular build.
| Platform | BRN-4 / HK-pattern |
| Caliber | 5.56x45 NATO |
| Barrel Length | 16.5 inches |
| Material | 4150 Chrome Moly Steel |
| Finish | Manganese Phosphate |
| Bore Profile | Medium |
| Twist Rate | 1-7 (Buttoned) |
| Chamber | 5.56x45 NATO (Chrome-Lined) |
| Muzzle Threads | ½-28 |
| Feed Ramps | M4 |
| Front Feature | Forward-Mounted Bayonet Lug |
| Manufacturer | Faxon (for Brownells) |
Yes. While designed for the Brownells BRN-4 platform, this barrel is also compatible with HK, 416, MR556, and MR223 receivers, making it a versatile choice if you're building across multiple platforms.
You'll need a Brownells BRN-4 16-inch gas block. The bayonet lug installs after the gas block using the same coil-pin method, so proper gas block fitment is essential.
Yes. The barrel features ½-28 threads, which accept the standard A2 flash hider found on the M27, as well as any common AR15-pattern muzzle device.
The M4 feed ramps and chrome-lined chamber are designed to work with a wide range of .223 and 5.56 NATO ammunition, giving you flexibility in what you run.
SKU: 167527886 • Weight: 2.25oz