Great upper - Bravo Company AR-15/M4 Complete Upper Receiver Assembly

I love the undersized extension. You will need to apply heat to seat your barrel in the receiver. I greased the barrel extension, applied heat to the receiver with a hair dryer, and the barrel slid right in. Definitely the most secure fit of any upper receiver I have ever used. Machining and finish are both excellent and BCM applies a dry film lubricant to the interior of the receiver. I am very pleased with this one and will definitely use this receiver for future projects.