An upper receiver is the upper half of a rifle. Every essential component of an AR-15 is contained in the upper receiver.
There are four types of AR-15 upper receiver, each with its own distinct design, advantages or disadvantages. The four main receivers are known as the A1, A2, A3 and A4 upper receiver, respectively. These receivers are named in the same way the military designated their M-4 assault rifles.
A Short Breakdown
The A1 upper receiver is the original and was developed for use by soldiers in the Vietnam War. A1 upper receivers feature a light profile barrel, forward assists, and a fixed carry handle. This model also includes a flip rear sight for elevation and is equipped with short and long-range apertures. The A1 receiver is accurate to within four-hundred-and-fifty yards.
The A2 receiver is an upgraded version of the A1 which was introduced in the eighties. Like the AI model, it is equipped with a fixed carry handle and a forward assist. Unlike the A1 model, though, the A2 model is adjustable for elevation up to six hundred yards, as well as for the effect of wind in deflecting a bullet, otherwise known as windage. The A2 barrel is also heavier, and features left-handed brass and rounded handguards, in contrast to the triangular handguards of the A1 model. The A2 has a twist rate of either 1:7 or 1:9.
The A3 receiver can be distinguished from the other models by its flat top configuration, featuring a detachable carrying handle. Many A3 models feature a Picatinny or Weaver rail to serve as a mounting platform for scopes or other accessories. It also includes forward assists and rifle cuts in the feed ramp. Some models come with a high rise configuration which provides a higher scope positioning.
Finally, the A4 upper receiver is very similar to the A3 upper receiver except that it includes M4 style feed ramps which complement the feed ramps found on the M4 barrel. The A4 model is the most common model on the market today.
In addition to these differences, you may ask yourself what the benefit of each rifle is.
The A1 upper receiver is lighter, so that might suit your physical needs better if you are a smaller person, unlike the heavier A2 model. The A2 upper receiver could better serve your needs if you live in a windy area with a higher elevation as it can be adjusted for elevation and windage. This is particularly useful if you are hunting in a windy season. The A3 could also be good in an elevated area with its high rise configuration. And the A4 model is good if you want to add an M4 barrel.
Types of AR-15 Uppers
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