Breek Arms BRK4420 Sentinel Caged Plan B Black Nitride Steel 1/2"x28 Threads 223 Cal/5.56mm

The Breek Arms Sentinel is a closed-tine flash hider engineered for 5.56 NATO and .223 Remington rifles built around Plan B suppressor mounts. If you're assembling a 14.5" barrel and need to meet federal length requirements through pinning and welding, or if you're building a suppressor-ready upper with a Plan B interface, the Sentinel delivers the flash reduction and compact profile serious shooters demand without the bulk of traditional brakes or flash cans.

Built from 4140 hardened steel with a nitride finish, the Sentinel's fully shrouded design keeps the muzzle signature low and minimal—critical for both daytime shooting and NVG-compatible operations. The caged tine construction suppresses flash while eliminating the snag points that open-design devices can catch on slings, body armor, or gear. At just 2.15" long and 2.2 ounces, it adds virtually nothing to your rifle's profile or balance, making it equally at home on a precision build or a duty-ready carbine.

Threading is 1/2"x28 TPI—the standard for modern 5.56 platforms—and the Sentinel is optimized to work seamlessly with Plan B fast-attach suppressor mounts, giving you flexibility to run it bare or add a can without changing hardware. If you're pinning and welding for a permanently attached solution on a short-barrel build, the geometry is straightforward and proven.

Key Features

• Fully shrouded, closed-tine design for effective flash suppression and snag-free profile
• Plan B suppressor mount compatible for quick-attach or pinned/welded setups
• 4140 hardened steel with black nitride finish for corrosion resistance and durability
• Compact 2.15" length and 2.2 oz weight for minimal impact on rifle balance and handling
• 1/2"x28 TPI threading—standard for 5.56 platforms
• NVG-optimized signature reduction for low-light and night operations

Specifications

Frequently Asked Questions

Will the Sentinel work with Plan B suppressor mounts?

Yes. The Sentinel is specifically engineered for Plan B fast-attach mounts, and it can be run with a suppressor or pinned and welded as a standalone flash hider.

Can I pin and weld this to a 14.5" barrel?

Yes. The Sentinel is designed to be pinned and welded, making it a popular choice for builders who need to meet the 16" federal minimum overall length requirement on shorter barrels.

What thread pitch does this use?

The Sentinel uses 1/2"x28 TPI threading, which is the standard for modern 5.56 NATO and .223 Remington rifles.

Is the Sentinel good for night vision or NVG setups?

Yes. The shrouded design and closed-tine construction are optimized to reduce muzzle signature in a way that's compatible with night vision systems, keeping your flash footprint minimal in low-light conditions.