To allow access to the Switchblock®, it cannot be covered up by a handguard. The longest handguard that can be used with a carbine gas system is 7″ and a 9″ for the mid-length, intermediate, and rifle length.
The Switchblock does not fit under a rail. Certain rails will fit behind it though.
The barrel ships with Switchblock® installed and the dowel pin in place. This barrel is designed for our Switchblock® that is 1″ long (INCLUDED). A standard front sight base is 1.9″ long and WILL NOT FIT. Barrel installation should be performed by a qualified gunsmith. Removal and installation of the Switchblock® is required to complete the assembly process.