Mkgs Complete Bolt Carrier Group Repair Kit .40 S&W

The CMMG Mkgs Complete Bolt Carrier Group Repair Kit for .40 S&W gives you everything you need to service or rebuild your rifle's BCG without waiting for a gunsmith. Whether you're doing routine maintenance, replacing worn components, or building a rifle from the ground up, this kit supplies all the essential parts in one package. It's built for shooters who take ownership of their gear and understand that quality upkeep extends the life and reliability of your rifle.

Each .40 S&W kit includes a complete bolt assembly paired with a carrier key system, firing control components, and springs—the critical pieces that see the most wear and stress during firing cycles. CMMG engineered this kit to simplify the rebuild process, so you're not hunting down parts individually or worrying whether incompatible components will work together. All parts are compatible and ready to go.

This is ideal for shooters who run .40 S&W platforms and want a genuine OEM repair solution on the shelf, ready when you need it. It's also practical for builders and folks who maintain multiple rifles and need spare parts on hand. No guesswork, no substitutes—just the real parts your BCG demands.

Key Features

• Complete bolt carrier group repair and rebuild components for .40 S&W
• Includes bolt, carrier key, firing pin, extractor, ejector, and all springs and pins
• Genuine CMMG parts engineered for reliability and durability
• Eliminates the need to source individual components separately
• Suitable for rifle maintenance, repair, and custom builds

Specifications

Frequently Asked Questions

What caliber is this bolt carrier group kit designed for?

This kit is specifically built for .40 S&W rifles. It's important to choose the correct caliber—CMMG also offers this kit in 9mm, so make sure you're ordering the .40 S&W version for your platform.

Can I use this kit to rebuild my rifle's BCG?

Yes. This complete kit includes all the major components needed to service or rebuild a bolt carrier group: the bolt, firing pin assembly, extractor, ejector, springs, pins, and the carrier key with screws. It's designed to give you a full set of parts in one purchase.

What's included in the box?

The kit contains: bolt, firing pin, firing pin retainer pin, RDB-style key with two key screws, bolt cam pin, extractor, ejector, ejector spring, and RDB bolt spring. These are all the essential components for a complete bolt carrier group assembly or repair.

Is this suitable for custom rifle builds?

Yes, this kit works well for builders and shooters assembling or upgrading .40 S&W rifles. Having a complete set of OEM parts ensures compatibility and simplifies the build process.