Brownells Brn-4/Hk416 Bolt Assembly

The Brownells BRN-4/HK416 bolt assembly is a complete, ready-to-install replacement bolt for your BRN-4 build or spare parts inventory. This fully assembled unit comes with extractor and ejector already installed, so you're not buying a pile of loose components—it's a functional bolt that cycles 5.56x45mm NATO and .223 Remington. Whether you're upgrading a parts rifle, maintaining a backup, or building from scratch, a quality bolt assembly is one of those investments that pays for itself the first time you avoid a malfunction downrange.

Brownells engineered this assembly with real durability in mind. The black nitride finish creates a hard, corrosion-resistant exterior that stands up to regular use and less-than-perfect storage conditions. The extractor features a black insert with an o-ring that locks in positive extraction—meaning your fired cases come out reliably, every time. Every bolt has been magnetic particle inspected and forged from 9310 tool steel, the same material you'll find in high-end factory rifles. That's not overkill; it's insurance against the one malfunction that matters.

If you run a Brownells BRN-4, HK416, or MR556 platform rifle, this bolt assembly is a straightforward drop-in. It's also a smart spare to keep on hand if you shoot regularly—bolts wear, and having a tested replacement ready means you stay in the fight instead of waiting for a gunsmith appointment.

Key Features

• Fully assembled with extractor and ejector—no additional parts to source
• Black nitride finish for durability and corrosion resistance
• Extractor fitted with black insert and o-ring for reliable case extraction
• 9310 tool steel construction, magnetic particle inspected for quality assurance
• Chambers 5.56x45mm NATO and .223 Remington
• Compatible with BRN-4, HK416, and MR556 rifles

Specifications

Frequently Asked Questions

Is this bolt assembly compatible with my HK416 or MR556?

Yes. This assembly is designed to work with Brownells BRN-4, HK416, and MR556 rifles. Always verify fitment with your specific platform before installation.

Does the bolt come fully assembled?

Yes. The extractor and ejector are already installed, so you don't need to source or assemble additional parts. It's ready to drop in.

What calibers does this bolt chamber?

This bolt is configured for 5.56x45mm NATO and .223 Remington.

What does magnetic particle inspection mean?

Magnetic particle inspection is a quality control process that detects internal and surface defects in steel components that might otherwise be invisible. It ensures the bolt meets durability and safety standards before it ships.