On our complete lower receiver assemblies and rifles, we are unable to stake the castle nut per mil-spec due to the endplate being made of aluminum. The aluminum will not displace material like a steel end plate does and chips off if attempted. After testing several different attachment procedures, we came up with our specific method of attachment. This method has been used on our rifles for several years without any issues. We also have hundreds of duty rifles in circulation with both Law Enforcement Agency’s and Military Personnel that have been put under intense usage in extreme conditions, experience zero failures with our method. To secure the Receiver Extension Assembly, we utilize VC3 Vibratite on both the Receiver Extension threads, and the Receiver Extension Castle Nut threads, and torque the castle nut down. VC3 Vibratite is designed to remain flexible, absorb vibration and the vibrational energy transferred between the threads of a mated fastener, preventing fastener loosening and loss of clamp load. With exceptional reliability, VC-3 holds parts in place even during extreme vibration and shock.