What Do Upper Receivers Do on a Firearm?

Upper Receiver

The receiver is a distinct feature of the AR-15 rifle series. This modular design is unique to the AR-15 family and is composed of the upper and lower receivers. The difference between the receivers is that the upper receiver, the top portion of the rifle, is responsible for the weight, accuracy, and performance, while the lower receiver houses the magazine and the firing mechanism found at the bottom part of the rifle. The upper receiver includes the bolt carrier group, the charging handle, and a metal compartment that houses the essential parts of the rifle. As part of the ‘upper receiver group,’ the barrel, glass block and gas tube, forward assist, rail system and hand guard, ejection port cover, muzzle break/compensator/flash hider are also included. In essence, the upper receiver is the top half of any AR-15 rifle and its parts can be customized to fit one’s preferences for hunting, home defense, or target shooting.

Components of the Upper Receiver

The upper receiver is considered as the ‘heart’ of a rifle because of the essential parts it contains such as the bolt carrier group and the charging handle. The upper receiver also includes the metal covering that houses the other parts of the AR-15.

The bolt carrier group (BCG) is composed of the firing pin, bolt, cam pin, extractor, and gas key. This group is responsible for loading the rifle and making sure that bullets are fired and ejected properly. Attached to the BCG is the charging handle, which, when pulled back, allows loading of bullets or clearing in case of a malfunction. The charging handle also permits loading the first round of a magazine if the bolt is closed. 

Upper Receiver Group

Included in AR-15 upper receivers are parts that form what is called the upper receiver group. Together with the BCG and charging handle, this all constitutes what is called a ‘complete upper.’

• Chamber—where bullets are lodged prior to shooting. 
• Barrel length—recommended to be 16 inches for an AR-15. This is responsible for the rifle’s accuracy. 
• Glass block and tube—together with the specific glass system types (rifle, mid-length, carbine) refer to where the gas port is located on the barrel. Gas travels from behind the bullet exiting the barrel, through the gas port, into the gas block, down the gas tube, and exits into the gas key on the bolt carrier. This gas pressure pushes the BCG in order to eject the spent case and chamber a new round. 
• Forward assist—ensures that the bolt closes properly and puts the bolt back in place. 
• Railway and handguards—protect the hands from heat during firing and can be customized to include lasers, flashlights, optics, grips, sights, and bi-pods as accessories.
• Ejection port cover—prevents dust and dirt from entering the BCG and ensures that the entire upper receiver is clean.

AR-15 Upper Receivers 

AR-15 rifles, or M-16, are the most popular sporting guns for civilians because of their ‘shootability’ and modular design. Gun ownership is legal in the United States and the AR-15 is one of the favorite rifles for civilians. Upper receivers can be customized to fit the preferences of the owner in order to fulfill its intended use for hunting, competitive shooting, or home defense. 

Upper receivers can be classified as either: 

1. a flat top upper with a picatinny rail, or 
2. a carry handle with fixed rear sight assembly on top. 

Regardless of the type of receiver, they can be stripped. A stripped upper receiver has no frills with no forward assist or dust cover. A stripped upper receiver is ideal for modification, as the plain metal casing allows the addition of parts and accessories. 

AR-15 uppers are caliber-specific and customization of this part allows convenient switching from one caliber to another. Parts of the upper receiver are likewise interchangeable, and you can fit parts from different manufacturers together. Some of the most common modifications include:

• Ambidextrous charging handles to increase handling proficiency and maneuver ability  
• Extended bolt release- clear jams and swap magazines faster
• BCG—lightweight and easier cleaning
• Barrel—replace worn out barrels or update current length for accuracy and increased velocity
• Muzzle breaks and compensators—reduce recoil and minimize vertical movement 
• Handguard—increase accuracy 
• Accessories—modifying pistol grip, buttstock, handguard, and adding optics (lights/lasers)

Custom AR-15 Upper Receivers

The AR-15 rifle series is a unique sports gun that allows customization of its upper receiver to enhance basic parts and add accessories that can provide enhanced shooting experience. Personalizing AR-15 rifles is beneficial because it allows one to enhance the capabilities of the rifle with the use of different parts and accessories. Customizing can increase accuracy and the overall performance of the rifle. Budget-wise, it is also practical to customize an AR-15 as it saves money and effort since it does not require additional paperwork when changes are made to an upper receiver.