AR-15 Upper Receiver Types

14th Oct 2016

AR-15 Upper Receiver Types

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, triangular handguard 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.

A typical A1 rifle features a light profile, 20-inch barrel with a 0.625-inch diameter and standard rifle barrel extension. The carry handle and rear sight are also integrated into the upper receiver.

Because the A1 is lightweight, it's often a popular choice for long shooting sessions, extended patrols and people with smaller physical statures.

AR-15 A2 Upper

The A2 upper was introduced as an upgraded version of the A1 in the early 1980s. It featured many enhancements that made the rifle more accurate and easier to shoot.

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 replaced the A1 windage drum with a dependable positive-click dial.

The A2 also includes a heavier barrel than its A1 counterpart, as well as a left-handed brass deflector 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.

The A2 upper features a beefed-up diameter of 0.75 inches toward the muzzle to improve accuracy when continuous shooting generates heat. It remains thinner toward the receiver to minimize weight.

While the A1 receiver allows ejected shell casings to fly near left-handed shooters' faces, the A2 receiver features a shell casing deflector just behind the dust cover for better protection.


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. This design optimizes it for use in elevated areas.

AR-15 A4 Upper

The A4 upper receiver is the most common model on the market today. 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.

The M4 barrel is the shorter version of the M16. Early feeding issues with the M4 were remedied with longer ramps, providing a more gradual transition from magazine to chamber. It's essential to use an A4 upper with an M4 barrel to get the best feed performance.


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.

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Purchase an AR-15 Upper Receiver From Wing Tactical Today

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, including Odin Works, Aero Precision, Noveske and Spike's Tactical. 

At Wing Tactical, we strive to get you the products you need as soon as you need them. That's why we offer next-day shipping options and 30-day hassle-free returns to minimize your wait times and give you the best possible service.

Check out our current AR-15 upper receiver inventory today! If you need assistance finding the right type of upper receiver for your needs, get in touch with our team of experts. Everyone at Wing Tactical is an experienced shooter, and we only recommend products we'd use on our own guns. We'll be happy to help you weigh the pros and cons of the different AR-15 upper receiver types to help you achieve the best rifle setup for your needs and preferences.

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