Roughly one in twenty Americans own at least one AR-15, according to a poll conducted by the Washington Post.  This is our Guide to Choosing the Right Upper Receiver for Your AR-15.

Armalite’s signature rifle has become the fourth most common gun in the world, behind only the AK-47, Mosin Nagant, and Mauser Gewehr 98. The flexibility and customizability of the AR-15 have made it popular with governments, police, and civilian enthusiasts alike.

Since AR-15s are so common, a lot of amateur gunsmiths get their start with one. Even new gunsmiths can swap parts, enabling them to choose the best AR-15 complete upper receiver for their use case. The AR-15 platform allows customization to almost any preference.

The process can feel daunting if you don’t know how to choose an upper receiver. How do you pick the best one for your needs? How can you be sure the upper receiver you select will support other parts you want to attach, such as sights, barrels, and handguards?

We’ll get you all the information you need. Keep reading for more details on stripped and complete upper receivers and how to choose the one that will suit your needs.

Stripped vs. Complete Upper Receivers

The AR-15 upper receiver connects all the parts you choose for the upper part of the gun to the lower part. It forms the core of the upper receiver group and significantly impacts the weapon’s performance.

Manufacturers offer two types of upper receivers. Stripped upper receivers include only the piece of metal designated as an upper receiver. Complete upper receivers have additional parts.

Common inclusions with complete upper receivers include the ejection port door and forward assist button. Some complete uppers, such as our offerings from Daniel Defense, also have barrels and other parts of the upper receiver group.

If you’re getting started in gunsmithing, the best AR-15 complete upper receiver for you will be a complete upper receiver. If you’ve been at this for a while or want to try your luck with more complex challenges, try starting with a stripped upper receiver and choosing other compatible parts.

Choosing the Best AR-15 Complete Upper Receiver

You need good information to choose an upper, even when you know the answer to “What is an upper receiver?” Because complete upper receivers include plenty of additional parts, you’ll need to look at the whole assembly to decide whether it suits your needs.

Parts in the upper receiver group besides the AR upper receiver itself include:

• Barrel
• Bolt carrier group (firing pin, bolt, cam pin, extractor, and gas key)
• Charging handle
• Ejection port cover
• Forward assist
• Gas block
• Gas tube
• Handguard
• Rail system

Experienced shooters and gunsmiths often have preferences already. Novices should consider some of the following questions when making a decision.

Carry Handle or Flat Top?

Sometimes upper receivers look different enough to make you wonder, “What is an upper receiver?” Some look more like the handle on a trash can, while others look like a flat piece of aluminum with ridges.

An AR upper receiver can have a carry handle or flat top design. These affect the gun’s overall appearance but add some functional considerations.

Despite the name, most shooters don’t carry their weapons by the carry handle. Instead, the carry handle serves as a rear sight assembly.

A flat top design adds a Picatinny rail instead of the carry handle, enabling it to mount various AR-15 accessories. Some shooters choose to mount a detachable carry handle on the Picatinny rail, opting to marry the iconic appearance of the AR-15 upper receiver with the flexibility of a rail.

This choice comes down to a combination of aesthetic and functional preferences. If you want AR-15 accessories that require a Picatinny rail, you’ll need a rail. Otherwise, go with what you think looks best.

What Length Barrel Do You Need?

To qualify as a rifle, an AR-15 needs a barrel length of at least 16 inches and an overall length of at least 26 inches. This length doesn’t include any AR-15 accessories like muzzle brakes or flash suppressors, such as the Griffin Armament suppressor we offer on our website. The ATF also has detailed rules regarding braces and collapsible stocks when measuring a rifle.

Any complete upper receivers you purchase, including the Daniel Defense upper options on our website, will have attached barrels at least 16 inches long. Many manufacturers also offer options with 18-inch or 20-inch barrels.

When you think about the barrel length you want, consider what you plan to use the AR-15 for. A shorter barrel length makes the rifle more maneuverable. A longer barrel will improve accuracy due to the higher muzzle velocity.

This trade-off makes the 18-inch barrel an unattractive prospect. Chasing two rabbits doesn’t often lead to catching any rabbits. Though if you want a shorter AR-15 and your other parts don’t add up to 26 inches without an 18-inch barrel, you might need it.

Go with the 16-inch barrel if you’re still at the phase of shooting where you’re asking, “What is an upper receiver?” The flexibility of the 16-inch barrel will work out for most shooters.

AR Upper Receiver Materials

Once you’ve considered the form factor, you should also consider the material for the receiver you want. Most types of upper receivers use aluminum, which offers a good balance of price, weight, and durability.

Consider titanium if you want a strong, light metal that will hold up under rugged conditions. While aluminum uppers will hold up under challenging conditions, a titanium upper makes an excellent long-term investment.

Consider a polymer upper if you’re looking for an incredibly light, maneuverable AR-15. Polymer uppers often use metal as reinforcement, making them more durable than they might sound at first.

Metal Upper Manufacturing Process

Those who choose a metal upper should decide between a billet, cast, or forged upper. These describe the manufacturing process used to create different types of upper receivers and significantly impact strength.

Manufacturers make cast uppers by pouring molten metal into a mold and finishing it. Cast uppers weigh much less than their forged or billet counterparts, but durability will take a hit. Cast uppers also cost a lot less, so if you want to build your own AR-15 on a budget, you might want to look into a cast upper with a good reputation.

Billet uppers represent a compromise between weight and durability. A billet upper starts life as a solid piece of metal before being shaped using a milling machine. Many competition shooters use billet uppers to reduce weight.

If you want exceptional strength, hardness, and resistance to metal fatigue, you want a forged upper. Forged uppers start as a larger piece of metal before the manufacturer hammers it into shape. This compresses the metal down, making it as dense as possible and giving it unparalleled durability at the cost of added weight.

As always, think about what you intend to use the weapon for and how often. If you’re an occasional range shooter, a cast receiver might hold up to all the use you’ll ever get out of it. If you expect to use the weapon a lot, a forged receiver might prove itself under conditions a cast or billet upper wouldn’t.

What About Caliber?

The upper of an AR-15 will affect what ammunition you can use. Since the caliber and the barrel width go hand in hand, a complete upper receiver will only allow you to shoot various calibers. A 5.56 receiver, for instance, will enable you to shoot 5.56mm and .223 rounds.

Make sure the upper receiver you buy matches the caliber you want to shoot. Note that not all states allow the use of all calibers for all situations. If you’re a hunter, make sure your state allows the use of your chosen caliber for taking the type of game you want to hunt.

Compatibility Issues

Almost all AR-15 uppers will fit onto AR-15 lowers, though sometimes issues can arise if you mix and match parts from different manufacturers. While they’ll almost always fit together and fire, parts can end up with imperfect fits. If you want to be sure things will work out, pairing parts from the same manufacturer will work best.

While all manufacturers adhere to military specifications, every now and then, something doesn’t add up quite right. Older Colt weapons have a different-sized pivot pin from a lot of the others and require an adaptor. Similar problems occur in many upper-lower pairings.

Enthusiasts call the most common compatibility failure “receiver slop,” as the fit between the upper and lower receiver has a little bit of give to it. Manufacturers produce products that address receiver slop, but some enthusiasts just put an earplug between the parts to put them in tension.

As with any high-ticket item, don’t be afraid to do a little research ahead of time until you’re confident you know how to choose an upper receiver. Other firearm enthusiasts may already have tried the upper you have your eyes on and have opinions about other parts that work well with it.

Whenever you perform customizations, ensure your new overall length still fits the legal standard for rifles. Customizing can satisfy a creative impulse, but the law is still the law.

Multiple Uppers for One Lower

Changing out a complete upper on an AR-15 doesn’t take a lot of time, and as long as you keep the same lower receiver and your overall length remains legal, it remains the same weapon in the eyes of the law. The modular nature of the platform contributes a lot to the AR-15’s staying power.  Choosing the Right Upper Receiver for Your AR-15 is a process.

Swapping out an upper can change a lot about a weapon. You can change the caliber, the barrel length, and the handguard with a quick swap. Once you get comfortable performing an upper swap, it can take less than a minute.

Do You Need a Background Check?

No. An AR-15 upper receiver requires no background check or licensing. A recent rule by the Bureau of Alcohol, Tobacco, Firearms, and Explosives looked at the possibility of classifying an AR upper receiver differently. The final rule clarifies that nothing changed, and AR lower receivers remain the regulated part.

If you purchase a lower receiver for your project (like the Rankin Industries lower we offer on our website), you’ll need to go through any registration and serial numbering steps required by local laws. The AR upper receiver does not require these steps either. When you review how to choose an upper receiver, you won’t need to worry about licensing issues.

If you don’t want to deal with that, you can get an 80% finished lower receiver, often called an “80 lower.” You will need to finish the milling of such a receiver yourself. Some areas require the registration of 80 lowers, so make sure to stay compliant with local laws.

Your Weapon, Your Way

The best AR-15 complete upper receiver for you depends on your use case and budget. You might even consider buying a stripped AR upper receiver and choosing all the other parts yourself. Half the fun of the AR-15 is that as long as you remain within your budget, you can try a lot of different things and see what you like best.

Whether you’re interested in learning about the AR-15 platform or purchasing your next weapon, come take a look at our website. We offer a wide range of AR-15 accessories and parts for new and experienced shooters, including complete upper receivers.

If you can’t find something that suits your needs, contact us and take advantage of our top-quality service and great prices.  We are happy to help you with Choosing the Right Upper Receiver for Your AR-15.