For those that are interested in building their own AR rifles, rather than buying a premade rifle, an assembled upper can save money and time.
First, they come with most if not all of what you need to mate to a lower to create a functioning rifle, and secondly, they save time and effort. Moreover, they don’t require an FFL transfer.
But just to make sure you have what you need to complete the build, read this.
The Upper Receiver Itself
The upper receiver is the part that “receives” the other components, like the barrel, handguard, and lower, hence the name.
When you buy an AR15 upper receiver, it’s either a billet or forged receiver. Forged receivers are forged from a block of aluminum, and billets are machined from them. Generally speaking, forged receivers are considered a little bit stronger.
The Barrel
A complete upper receiver will also come with a barrel, the chambering of which will determine the specifications of the rest of the build.
Barrels can be either stainless or CMV; stainless barrels are low maintenance, but as a general rule CMV barrels are considered stronger and more durable overall.
Pay attention to barrel length, as it will impact FPS rating at the muzzle, as well as accuracy along with weight and handling.
You may also want to choose a fluted barrel, which will not only be lighter, but which will be better at dissipating heat than a barrel that is not fluted.
A Gas System
A complete upper receiver should also come with a gas system pre-installed on the barrel. The system consists of a gas block and tube.
The gas block shuttles gas out of the barrel after the bullet passes it, which gets siphoned off to the gas tube, and which then travels back to the bolt carrier group’s gas key.
One of the benefits of buying an assembled upper is that it will come with this system pre-installed, so you won’t have to do that yourself.
A Muzzle Device
An assembled upper will come with a barrel and should come with a muzzle device, which in almost all instances will be a flash hider.
A flash hider is a device that is designed to obscure the muzzle flash so as not to temporarily blind the shooter, keeping the sight picture clearer for faster, more accurate follow up shots.
If you ever remove this muzzle device from the barrel, make sure you either replace it with a different one, such as a suppressor or a muzzle brake, or else install thread protectors.
A Handguard
A complete upper receiver for an AR15 or similar sporting rifle will also come with a handguard. What type it comes with, however, may vary.
Some may come with tropical handguards that don’t have any attachment points, but likely the majority of them will come with Picatinny, or “Pic” rails that have been a staple for decades.
That said, while Pic rails are still very common, and while there are many attachments that are compatible with them, modern alternatives, like KeyMod and M-LOK rail systems, are lighter and more comfortable to use.
What’s Sometimes Included (But Not Always)
There are some parts that may or may not come with an assembled AR15 upper, but which are still needed to complete a functioning rifle.
Bolt Carrier Group (BCG)
The bolt carrier group, also known as the BCG, is the heart of the rifle, and contains the gas key, firing pin and spring, extractor and ejector. Without a bolt carrier group you cannot assemble a functioning rifle.
Forward Assist
The forward assist is a simple device like a plunger or button that can be used to get the bolt carrier group to completely close and lock if for any reason it does not return to battery. This functionality gives it its name. While it is an important and valuable part, a forward assist is not necessary to complete a functioning rifle.
Ejection Port Cover
The ejection port cover, also known as a dust cover, is literally just a cover that shields the ejection port from dust and particular matter ingress whenever the action is opened. Unlike most of the other parts mentioned here, a rifle can function even if the ejection port cover is absent,
Charging Handle
The charging handle is the part by which the action may be manually manipulated, such as to charge the action (hence the name) or to clear jams and other malfunctions. Many assembled uppers come with them but not all do.
Explore Assembled Uppers and More Here
In the market to start a new rifle build? Explore our collection of assembled uppers for a variety of calibers, along with AR parts and more here and if you have any questions get in touch with us at Sales@MCSGearup.com.