By AT3 Tactical
The AR-15 upper receiver (often simply referred to as an “upper”) holds and protects many of the most important components on your AR-15.
There are many types of uppers on the market, and it’s vital to understand the differences between uppers when building or buying an AR-15.
Different Types of AR-15 Uppers
Your receiver will be either a “flat top” or a “carry handle” upper.
The flat top has a Picatinny rail on the top of the upper, while . . .
Carry handle uppers feature a fixed carry handle on the top of the upper. (Note: the carry handle doubles as a rear sight assembly, so you probably shouldn’t use it to carry your weapon).
You’ll often hear of receivers referred to as being A1, A2, A3, or A4 receivers. We have a great article that explains this in detail, but generally the big difference is flat top vs carry handle.
The other big consideration is the forward assist button. Some uppers have them, some don’t. It’s debatable whether this button is really necessary for most shooters, but just remember all military M16 and M4 rifles have them for a reason – a tap on the forward assist will assure that the bolt is fully forward and seated in battery.
So which upper is right for you? We recommend a flat-top upper with a forward assist for most AR-15 builds – the Picatinny rail provides versatility (you can always add a carry handle to a flat top if that’s your thing), and it’s the most popular style of upper, which means that they’re cheap and plentiful.
Upper Receiver Construction: Forged, Billet or Cast
Upper receivers can be made from various metals, but aluminum is by far the most common. Beyond the material being used, the construction of the upper is determined by the manufacturing methods used.
Forged Upper Receivers
Forged metal uppers provide the ideal grain structure or orientation that produces the best mix of mechanical properties like hardness, fatigue limit, specific weight and others, but they’re denser and heavier. A forged upper is created by “forging” (hammering) the upper into the proper shape and then typically it’s finished on a CNC machine.
Billet Upper Receivers
The billet receiver is made by milling a solid hunk of metal with a CNC machine until it’s the proper shape. Billet metal has similar mechanical properties to forged, but they’re generally less dense and lighter at the expense of a little strength in the material.
Cast Upper Receivers
Cast metal is the lightweight of the group, but it also offers the least amount of relative strength. But since it’s usually the lightest upper, sometimes cast is more than “good enough.” Cast uppers are made by pouring molten metal into a form (also known as “die casting”). Typically some finish work is then done with a CNC.
Stripped vs Complete Uppers
A stripped upper consists of only the upper receiver itself, basically a shell that needs to be completed.
A completed upper will come with the ejection port door and the forward assist button installed.
You will also see “complete upper assemblies,” which include the completed upper along with the charging handle, barrel, handguard, and possibly the bolt carrier group.
So basically, the stripped upper is a single part – the upper receiver. A “complete upper” will include a few more parts. And a complete upper assembly is a full upper-half of an AR-15 rifle. Just attach it to a lower receiver and it’s ready to fire.
One Last Tip
If there’s anyone that knows the AR-15 platform, it’s the US military. As a special offer for our readers, you can get the Official US Army Manual for AR-15/M4/M16 right now – for free. Click here to snag a copy.
This article was originally published in AT3 Tactical AR Academy and is reprinted here with permission.