CMMG 55CA9CB Receiver Extension Castle Nut MK4

CMMG Receiver Extension Castle Nut MK4

The CMMG 55CA9CB is a precision-engineered castle nut designed for AR-15 buffer tube receiver extensions. This component plays a critical role in your rifle's function and reliability.

Purpose and Function

The castle nut secures your buffer tube to the receiver extension, ensuring a tight, rattle-free fit. Proper installation of this nut is essential for consistent cycling and reliable operation of your AR-15.

Key Features

• Durable Construction: Manufactured by CMMG, a leader in AR platform components since 2002
• Matte Black Finish: Professional appearance that resists corrosion
• AR-15 Compatible: Fits standard AR-15 receiver extensions
• Precision Fit: Engineered for proper lock-up with staking for permanent installation

Installation Notes

This castle nut should be installed with the notches aligned with the receiver extension holes, then staked in place to prevent loosening. Proper staking is critical for maintaining zero and ensuring reliable function.

Whether you're building a new rifle or replacing a worn component, the CMMG castle nut delivers the quality and reliability you expect from a manufacturer dedicated to AR platform excellence.