AR-15 Upper Receiver Types

AR-15 Upper Receiver Types

14th Oct 2016

If you are brand-new to the world of the AR-15 rifle, you may be confused about the many different AR-15 receiver types. One way to gain a better understanding of what a receiver actually does is to compare it to the chassis of an automobile. As with a chassis, all essential AR-15 parts are built onto the receiver. The AR-15 receiver consists of upper and lower portions — the latter of which is the legally controlled, serialized part. In this post, we will explore the various AR-15 upper receiver types, including the AR-15 A1, A2, A3 and A4.

AR-15 A1 Upper

The A1 is the original AR-15 upper receiver version. Developed in the 1960s, the A1 was installed on the M-16 A1 rifles used by soldiers in the Vietnam War. Key A1 features include a light profile barrel, forward assist and a fixed carry handle. There is also a flip rear sight that adjusts for windage, but not elevation. The rear sight is also equipped with short- and long-range apertures. The A1 provides a 1:12 twist rate. In general, the AR-15 A1 upper provides accurate firing within approximately 450 yards.

AR-15 A2 Upper

The A2 upper was introduced as an upgraded version of the A1 in the early 1980s. As with the A1, the A2 is equipped with a fixed carry handle and a forward assist. However, the rear sight of the A2 is more advanced and is adjustable for elevation (generally up to 600 yards) as well as windage. The A2 also includes a heavier barrel than its A1 counterpart, as well as a left-handed brass and rounded handguards (as opposed to the triangular-shaped handguards of the A1). Depending on the manufacturer, the A2 features a twist rate of either 1:7 or 1:9.

AR-15 A3 Upper

The A3 upper receiver offers a flat top configuration featuring a detachable carrying handle. Depending on the manufacturer and model, an A3 upper may be equipped with either Picatinny or Weaver rail to serve as the mounting platform for scopes and other accessories. The A3 also includes forward assist and rifle cuts in the feed ramp. Some A3 models are available in a “high-rise” configuration that extends the base upward, providing a higher scope positioning.

AR-15 A4 Upper

Like the A3, the A4 is a flat top upper receiver, and both are very similar in their design and construction. The main difference between the A3 and A4 is that the latter includes M4-style feed ramps, which serve the purpose of complementing the feed ramps found on an M4 barrel.


While we have discussed some of the history of upper receiver types in this post, the A1, A2, A3 and A4 classifications of upper receivers refer to how the military distinguished each of the M16/M4 model setups. Nowadays when people refer to an A2- or A4-style upper receiver, this is not in reference to the barrel length or twist rate, and instead only refers to whether or not the upper receiver has a fixed carrying handle/forward assist. On the market today, you will most likely find A4-style upper receivers with variety of handguard and barrel options for customization.

Wing Tactical is your one-stop source for all your AR-15 accessories, including  upper receivers. We offer a wide selection of high-quality AR-15 uppers from leading manufacturers. Check out our current AR-15 upper receiver inventory today!

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