The AR-15 is one of the most popular rifle platforms available, renowned for its adaptability to suit a vast array of applications. The design stands out amongst other platforms, using two dedicated receivers: an upper and a lower.
While the lower receiver houses many of the rifle’s controls like the trigger and safety selector, the upper receiver is arguably the heart of the rifle, serving as the primary backbone of the rifle while determining much of how the rifle performs. No matter if you’re new to owning and building AR-15s or if you own a few already, understanding what to look for in an upper receiver is paramount to building a rifle that emphasizes durability and reliability.
Understanding AR-15 Upper Receivers
The AR-15’s upper receiver is a crucial component that serves as the mounting hub for the barrel, handguard, and optics once assembled. It makes up the top half of the rifle and houses critical components like the bolt carrier group (BCG) and charging handle.
Types of AR-15 Upper Receivers
AR-15 upper receivers are available in several configurations: stripped, assembled, barreled, and complete.
Stripped uppers are the most bare-bones option, including only the upper receiver itself. These types of uppers are the best choice if you want to customize yours completely, since they don’t come with a forward assist or dust cover. There are a lot of aftermarket options available for upper parts, and if you already plan to customize your build, they’re a solid choice to go with.
Assembled uppers come with the dust cover and forward assist pre-equipped. Many enthusiasts don’t change the mil-spec forward assist and dust cover on their upper anyway, so this upper offers a nice blend of customization and convenience.
A barreled upper receiver has the barrel and gas assembly already installed on the rifle. Although they appear complete, they lack a BCG and charging handle, giving you the freedom to choose which ones go into your build. Also, most of the time, they come equipped with a free-floating handguard, but this can vary depending on the manufacturer.
Complete uppers come with all the components necessary for their construction, making them the most convenient choice that’s ready to be paired with a complete lower. Depending on the manufacturer, they can come with upgraded components as well, with some options including sights, upgraded BCGs, lightweight handguards, or other parts as well.
Factors to Consider When Choosing an AR-15 Upper Receiver
Quality and Material
Whenever you’re selecting an upper receiver for your AR-15, the quality of it and the materials it’s made of are paramount to ensuring the integrity of your build. Upper receivers are mostly made of 7075-T6 aluminum, which is known for its light weight and stress resistance. Historically, another common material used is 6061-T6 aluminum. While not as strong as 7075-T6, it’s still incredibly lightweight and durable enough to stand up to adverse conditions and extraneous use. Generally, you should almost always prefer a 7075 receiver unless you’re intentionally building on an older 6061-T6 receiver (such as rebuilding a classic rifle).
Notably, there are two main receiver types, those being forged and billet. Forged receivers are the most common, made from a single piece of aluminum that’s been forged into the correct shape. Billet receivers are made from the same materials, but instead of being hammered into shape, they’re milled down from a larger aluminum block. Because of this, billet receivers take longer to make and are often more expensive compared to standard forged uppers, but they offer better fitment and can come with added features. We’ll touch more on this below, but billet receivers offer notable benefits.
Desired Features and Customization
As we mentioned, manufacturers offer upper receivers with various features. So, if you’re shopping for a complete upper, regardless of what you’re looking for, it’s relatively easy to find one that already has the components you’re looking for. If not, you can easily build out a stripped or assembled upper to include all your desired components.
The AR-15 is one of the most modular and adaptable rifle platforms around, and all the parts on an upper receiver can be swapped out for different ones, giving you complete control over your build. If you’re building a rifle for competition, you could opt for lightweight components as they offer better agility than standard ones. If you’re focused on building out a rifle for home defense or duty, you can choose components that are more durable and offer better longevity.
Another point of consideration is your rifle’s caliber. You can use multiple uppers for one lower. As such, there are many .300 Blackout uppers available, allowing you to easily swap between the two calibers without needing to buy another rifle.
Regardless of whether you choose to build or buy, there are dozens of high-quality manufacturers producing thousands of upper receivers, so no matter what your rifle’s purpose is, there’s something for everyone.
Parts Compatibility
AR-15 receiver designs generally have consistent specifications to ensure that different upper and lower receivers fit together. Premium manufacturers usually offer tighter tolerances on their uppers, reducing receiver wobble, and ensuring that each upper part is securely fixed in place. Receiver wobble occurs when there’s extra space in between the upper and lower receivers when they’re attached to each other. It doesn’t pose much risk to your rifle, but the extra space can be a place for dirt to enter the rifle when in rough conditions, making tighter tolerances sought-after by many.
If you’re looking for the best fitment possible, billet receivers will provide you with the tightest fitment, so long as they’re a matched set. When shopping around for uppers, you’ve more than likely come across one of the various receiver sets available that come with both a billet lower and upper receiver. These receivers often have tighter tolerances as they’re machined specifically for use with one another, providing you with optimal fitment for your build while still being compatible with all standard AR-15 components.
Keep in mind that manufacturers can include their own unique features that alter its compatibility. Upper receivers like the Aero Precision M4E1 Enhanced Upper Receiver have a reinforced handguard mount that’s only compatible with Aero Precision’s Enhanced and Quantum series handguards. Upper designs can vary, but so long as you research the upper receiver to make sure it’s compatible with your build, you’ll be good to go.
Budget Considerations
Upper prices can vary drastically depending on the manufacturer and their included components. For instance, an upper with standard mil-spec components is going to be far less expensive than a Daniel Defense upper with their RIS III handguard, CHF barrel, and upgraded components.
Fortunately, there are several uppers available that offer high-quality components at budget-friendly prices, with Aero Precision and Andro Corp being some popular options. For more premium options, Sons of Liberty Gun Works, Geissele, and BCM uppers being some of the most prominent choices. Before you make a final decision, though, it’s important to take time to evaluate your needs and your specific purpose for owning an AR-15, as this will help you narrow down the options that are available to you.
Assembling an AR-15 Upper Receiver
If you’re opting to build an upper receiver instead of buying a complete one, you’ll need the proper tools and the knowledge to do so. Ideally, you should have a bench vise for upper vise blocks, a proper AR tool, punches, and a soft-headed mallet. For the sake of convenience, we recommend picking up a firearm tool kit before you begin assembling your upper.
Whether it’s your first time building out an upper, or if you’ve done it a thousand times, we recommend looking at our guide on how to assemble an AR-15 upper receiver. It goes over the full process step-by-step and has a lot of solid info and best practices for ensuring your build goes smoothly.
Maintaining your Upper Receiver
With your upper receiver assembled, you’ll need to know how to maintain it and take care of it so that it continues to function as it is supposed to. Cleaning and regularly inspecting the components for any excess wear should be done every so often to keep it running. An AR-15 cleaning kit will have all the necessary cleaning tools you need, while a good cleaning agent like CLP is all you’ll need for routine maintenance.
Start by field stripping the upper. If your rifle is already complete with your upper mounted onto a lower, remove the magazine and check both visually and physically that your AR-15 is unloaded. Next, push out the pivot pins to separate the upper and lower halves and pull on the charging handle to remove it along with the BCG. With these parts out of the rifle, you can clean them and the barrel easier.
Clean each part with CLP or another solvent to remove any carbon that’s built up on them. Next, with a bore snake and cleaning pads, clean out the barrel until you can run a cleaning pad through the barrel without it picking up carbon. After cleaning, you can lubricate and reassemble your firearm. At this point, perform a quick function check just to make sure everything is working properly, and if it is, you can store it for later use.
Ideally, you should store your rifle or upper in a gun case when it’s not in use. It’ll keep it safe from exposure to humidity and dust, preventing core components like your barrel from rusting, while also preventing dust and debris from building up on any exposed oil. To err on the safe side, it’s important to be mindful of where you store it. For instance, if where you store your rifle is close to a shower in your home, exposure to steam can cause your rifle to rust over.
Conclusion
Your upper receiver plays a crucial role in your AR-15 build. As such, understanding the nuances and core differences between upper models is paramount to ensuring that the end-result of your AR build is fine-tuned for performance.
Remember that different uppers offer their own distinct advantages. If you want an extremely specific build, complete with the parts and components of your choice, a stripped or assembled upper receiver is going to give you the greatest freedom of choice for your build. On the other hand, if it’s your first build or you just want some simplicity, barreled and complete uppers are the move.
Regardless of which option you end up going with, it’s important to make sure that you research all the options you have. The quality and features of your upper receiver play a pivotal role in the overall functionality of your rifle, and with the right one, it will serve you well for a long time.
There is a lot that goes into creating an ideal setup for your AR-15. If you’re on the fence about how to build yours, our guide on the best AR-15 goes in-depth on all the key parts and components that shape your rifle’s performance.
