A rifle upper receiver is an essential component of the AR-15 rifle and similar style models like the M4 and M16. It serves as the main housing for the bolt carrier group, barrel, and other internal parts. The upper receiver is what holds the lower and upper parts of the gun together and is responsible for feeding the cartridges from the magazine into the chamber. It is usually made from aluminum or polymer and can be either flat-top or carry handle style. The flat-top style has no iron sights and requires a scope or aftermarket iron sights to be mounted on top, while the carry handle style features built-in iron sights. Additionally, most upper receivers come with a charging handle that allows you to cock the rifle without having to pull back the bolt. This can be beneficial in situations where you need to chamber a round quickly or in a hurry. Upper receivers also come with a variety of different finishes including anodized, Cerakote, and various camo patterns. When purchasing an upper receiver, it is important to make sure that it matches your lower receiver and also that it is compatible with your barrel. With all of these features, a rifle upper receiver is an essential component for any AR-15 rifle build.