Best AR-15 Upper Receivers: The Complete Buyer’s Guide

| Last Updated:
August 10, 2023

For most civilians, our first contact with shoulder-held firearms comes in the form of traditional wood-stocked rifles.

Typically, the wooden stock is attached with a metal receiver that everything attaches to it, including the barrel, trigger group and handguard.

However, with the introduction of the AR-15, one of the most popular rifles in use today, many traditional concepts changed, from the incorporated materials to the rifle configuration.

Comparison Chart of the Best AR-15 Upper Receivers

  • M4 Feed Ramps and .250 Takedown Pin Holes
  • Flattop With Rail Already Installed
  • Amazingly Affordable Price
View Latest Price →
  • Complete Upper Receiver for 300 AAC BLK
  • 4150 Chrome Moly Vanadium Body
  • Full-Length Rail on The Receiver and Handguard
View Latest Price →
  • Fully-Assembled Forward Assist and Port Cover
  • Dry Film Lubrication on the Inside to Resist Wear
  • Easy to Install and Works With Many Guns
View Latest Price →
  • Fully-Assembled and Complete Upper With Barrel
  • Includes a 308 A2 Flash Hider
  • Full-Length Rail on The Receiver and Handguard
View Latest Price →
  • Complete Upper with 1:8 Twist Barrel
  • Long Handguard With Keymod System
  • Good Value for Money
View Latest Price →
  • Complete Upper Assembly With Barrel and Flash Hider
  • Includes a Free-Float Handguard
  • Receiver and Handguard Have Same Level Rails
View Latest Price →

What’s a Gun’s Receiver and Why Does an AR-15 Have Two?

One of the distinguishing features from traditional guns is the AR-15’s modular design with multiple receivers, enabling it to be split into two distinctive and fully self-contained halves. Actually, this feature has persuaded shooters to start calling the upper half the "upper receiver" and lower half the "lower receiver” for lack of a better term.

The bottom half, or lower receiver, contains all the parts needed to fire an AR-15 such as the trigger group, magazine well, buffer assembly, shoulder stock and pistol grip.

According to the laws of many countries the gun receiver is the part of the firearm that carries the serial number. As such it’s the controlled component. That means it’s the part you need licensing for (where a gun license is required).

 In the case of the AR-15 the lower half is serialized and considered the legal receiver. The upper receiver doesn’t need to be licensed since it’s considered just a part and not the working core of the gun.

What Are The Components of an Upper Receiver?

The upper receiver can be simply seen as the upper half of the AR-15 rifle. The upper receiver comprises of the bolt carrier group, charging handle, ejection port cover, forward assist (if included) and the metal housing which encapsulates and combines all these parts. The barrel, gas block, handguard, sights and carry handle are also considered its parts, but then the upper is called the ‘upper receiver group’.

The BCG (bolt carrier group) is responsible for the cycling and firing of the rounds. It includes the bolt, ejector and the firing pin. The forward assist is responsible for closing the bolt if it doesn’t close properly. The ejection port cover protects the inner components from any dirt or debris.

The receiver can either be flat-top with rails or have a carry handle. Upper receivers are caliber specific and play an important part in the accuracy of the rifle. An upper receiver is joined to the lower using two take-down pins. Since most AR lower receivers are multi-cal, you only need to change the upper to switch the caliber of the rifle.

The reasons for customizing are many. Buying a complete upper receiver allows you to quickly and easily replace some of the key parts of your gun. One advantage of swapping out AR-15 upper receivers instead of buying a complete rifle in the configuration you want surely is the price. While the factory AR-15 price tag is ranging from $800 to $1,500, complete upper assemblies can be found for anywhere from $300 to $900. If you want, you could have various upper receiver setups that you just need to swap out depending on how you’ll be using your gun on a particular day.

The term “complete upper receiver” sometimes can be a bit confusing because there’s no industry standard for what “complete” means. Some vendors offer a receiver with only a dust cover and forward assist installed. In other cases complete uppers may consist of the handguard, charging handle and even the BCG (bolt carrier group) and barrel. As earlier mentioned, you need to research manufacturer's ads thoroughly and check the full parts list of components to ensure you're getting everything you need.

A stripped upper receiver, on the other hand, does not include the forward assist or dust cover. You have to buy and add those yourself. It adds more complexity but also a higher degree of customization to your gun.

Types of Upper Receivers

Upper receivers can be classified into several different types, depending upon their design. Each of the receivers can be used for specific purposes depending upon the convenience of the shooter.

Stripped vs. Complete Uppers - What’s the Difference?

A receiver can either be complete or stripped. Generally, a complete receiver includes all the components with the receiver block. Whereas a stripped receiver is just the outer case. However, the definition of complete and stripped receivers differs from manufacturers.  

A complete upper receiver often comes with a pre-installed barrel and handguard, so you don’t have to scour the markets for finding compatible parts. On the other hand, a stripped receiver allows you to choose each individual part according to your personal discretion. Thus resulting in a more customized rifle. Some people like to use only the best components from different manufacturers, and in such cases, a stripped receiver is a better choice. Oh, and don’t forget the price difference as well.

What is a Side Charging Upper?

AR-15 rifles feature a rear charging handle located at the rear end of the rifle. Charging such a handle can be difficult in situations where you don’t want to take the eyes off the sights. A side charging AR-15 upper features the charging handle on the side of the receiver. Just like an AK-47 or Ruger 10/22. A side charging upper doesn’t have a forward assist as well.

What is 9mm AR-15 Upper?

A 9mm AR-15 upper receiver allows you to shoot 9mm cartridges through your rifle. Such uppers are quite compact in size and generally used for build pistol style AR-15’s. 9mm uppers are a good alternative for building compact AR-15 rifles which are ideal for self-defense. Plus they allow you to shoot less expensive ammunition and are allowed at most indoor shooting ranges.

What is a Left Handed Upper?

A left-handed upper is designed for left-handed shooting or shooters. It has the forward assist and the ejection port on the left-hand side of the receiver. The position of the charging handle may still be on the rear unless it is a side charging upper.

Qualities of an Excellent Upper Receiver

A good product has to have some qualities which make it different from its competitors. Before you buy an AR-15 upper receiver, you must consider looking at these factors.

Material and Quality

The very first characteristic to look for in an AR-15 upper is its manufacturing type. A receiver can either be forged, billet machined or cast. Forged receivers are a bit on the heavy end, but they are the most sturdy and durable. Machined receivers, on the other hand, are lightweight, but not very durable in the long run. Cast receivers sit somewhere between these two. Other than this, an upper should’ve been properly inspected for quality using HPT or MPI methods.


A good upper receiver must be complete with all components if it is a complete upper. This ensures that you don’t have to search around for finding appropriate components on the market. It is always a good option to choose uppers with already fitted rails.


The handguard of your receiver can either be free-floating or connected to the barrel. Free-floating handguards are generally a better option for the accuracy of the rifle. Plus you should also consider the type of mounting mechanism (key-mod, M-Lok, Rails) depending upon your needs.

Gas System Length

Another aspect to consider when choosing a complete upper is the gas system length. AR-15’s have three types of gas system lengths. Rifle, mid-length, and carbine. Rifle length is good for long-range weapons, whereas carbine length is good for home defense and CQB rifles. The gas system combined with a 16-inch barrel is a good and versatile compromise among all three.

Review of the Best AR-15 Upper Receivers

Following qualities of an ideal AR-15 upper, we searched the online market to find the best uppers suitable for everyone’s needs. Some of the uppers reviewed here are complete whereas some are stripped. All these receivers are best in their class, and available at an economical price.

Best Complete Overall:
PSA 16" Carbine Length 5.56 NATO 


  • 1:7 Twist Rate Barrel
  • Full-Auto Bolt Carrier
  • Durable and High-Quality Design
  • Pre-installed Front and Rear Sight


  • Limited Rail Space

This complete upper receiver from PSA has been designed to work effectively and flawlessly. The receiver has been forged from 7075 T6 aluminum with a full-auto bolt manufactured from 158 carpenter steel and a top charging handle. The upper receiver has a carbine length gas system, which offers a good mix of capabilities between a long range rifle and a CQB tactical carbine.

The upper includes a 16-inch barrel, with an amazing twist rate of 1:7 and melonite finish. The barrel has ½-28 threads on the muzzle to accept different muzzle devices. The gas block has an F-marked front sight base, which resembles the classic design of AR-15 rifles.

The forend of the upper features Magpul MOE black handguard, and the rear end features a Magpul MBUS Rear Flip-Up Sight. The receiver has been railed at the top to accept most optic accessories.

Bottom Line

This complete upper from PSA offers the right mix between quality and price. The upper has a full auto bolt carrier, and amazing barrel and pre-installed sights. Pretty much everything that’s required for plug-n’-play.

Best Stripped Overall:
Brownells - AR-15 M4 Stripped Upper Receiver


  • M4 Feed Ramps
  • Allows Full Customization
  • T-Marked Picatinny Top Rail
  • Forged From 7075 T-6 Aluminum
  • Fair Pricing Respective of its Quality


  • None

The AR-15 stripped receiver from brownells has been forged from 7075 T-6 Aluminum. One of the most durable materials to manufacture receivers. The upper has been Type III hard-coat anodized, pertaining to the military specifications.

The nooks and crannies of the upper receiver have been machined to mil-spec dimensions to ensure compatibility with most aftermarket parts. The upper also features M4 feed ramps to aid in chambering during high rates of fire.

This is a true stripped upper with only the receiver block and no other components. Which allows you to customize the upper the way you like. The receiver also features a picatinny rail on the top with painted markings for easy switching of optics and accessories.

The upper is aesthetically pleasing and easy to install, plus it works with many guns. It has a good matte black finish and does not scratch easily.

Bottom Line

The AR-15 receiver from Brownell’s is a versatile upgrade to your rifle. It is ideal for all applications associated with the AR-15 rifle including hunting, competition, and self-defense.

Best Complete Runner-up:
PSA 16" Mid-Length 5.56 NATO 1/7 Nitride 15"


  • Lightweight Upper
  • Full-Length Rail on the Top
  • Dead-on Accurate Up To 600 Yards
  • Melonite Coated Barrel With 1/7 Twist
  • M-lok Handguard for Mounting Multiple Accessories


  • None

This is our runner-up for the best complete AR-15 upper receivers on the market. It features a forged upper receiver with a full-auto bolt carrier made from Carpenter 158 steel. The upper comes complete with all the components and features of a mid-length gas system. The A2 profile barrel has a chrome-moly vanadium construction and a melonite finish for durability.

The major feature of this complete upper is the M-Lok handguard and the full-length rail. The handguard allows you to mount different accessories, meanwhile facilitating quick cooling of the barrel. The top rail running from the handguard to the receiver offers a large amount of space to mount multiple optics. The barrel of the upper is quite accurate and shoots precisely up to a range of 600 yards.

Bottom Line

The full-length rail and m-lok handguard make the upper more admirable and efficient. The mid-length gas system is appropriate for long-range shots in the 600-700 yards range. Additionally, all PSA products are covered by an unlimited lifetime warranty, so there’s no harm in buying it.

Best Stripped Runner-up:
Aero Precision - AR-15/M16 Stripped Upper Receiver


  • Works With Many Guns
  • Sharp and Precise Design
  • Aesthetically Pleasing Finish
  • Good Mix of Durability and Lightweight
  • Compatible With Most Standard AR Lowers


  • None, unless there’s a manufacturing flaw.

The Aero Precision stripped receiver has been machined from a billet of aluminum. Thus imparting a sharp and precise finish to it. The receiver features a good mixture of durability and lightweight, due to its material and manufacturing process.

The type III hard coat anodized finish provides exceptional wear resistance against most weather and field conditions. The receiver is available in Black, Cerakoted OD Green, & Cerakoted FDE finish, so you have multiple options to choose from.

The top of the rail features a picatinny rail with T-marked slots for proper placement of optics and estimation of rail space. The end of the picatinny rail (where the charging handle starts) bears an American national flag, which also adds to the aesthetics of the rifle.

The receiver has a forward assist cavity and an ejection port (without cover). The receiver gives you a full hand to customize your upper receiver the way you want. The receiver features M4 feed ramps and .250 take-down pin holes. Thus making it compatible with most mil-spec AR lowers.  

Bottom Line

The Aero Precision Strippe Upper is an aesthetically pleasing and lightweight piece of equipment for building your AR. The upper delivers exceptional value for money and is ideal for tactical and competitive applications.

Best Complete for the Money:
PSA 16" Mid Length 1/7 Nitride 15"


  • M-Lok Rail Handguard
  • Durable Full Auto BCG
  • Lightweight and Durable
  • Complete Upper With BUIS
  • Drop-in Installation and Ready to Fire
  • Melonite Coated Barrel With 1:7 Twist


  • Doesn’t Work Very Well With Cheap Ammo

This complete upper from Palmetto State Armory is a ready-to-fire upper. It features a Forged 7075 T-6 aluminum construction and M4 type feed ramps. The upper has all the accessories attached to it including the forward assist, bcg, charging handle, ejection port cover, top rail, barrel, handguard, A2 muzzle device, and BUIS.  The 16-inch barrel has a twist rate of 1:7 and is ideal for tactical and hunting applications. The barrel has been made from Chrome-Moly Vanadium and features a nitride lining on the inside.

The upper has a mid-length gas system that offers a good balance of range and muzzle velocity. The handguard has a lightweight M-Lok rail which can be used to mount compatible QD swivel based accessories. The muzzle of the upper is threaded to accept any aftermarket muzzle device with compatible threads.

The full-auto bolt carrier group is durable and will withstand strenuous firing sessions. The best and extra addition to the complete upper is the backup iron sights. The total length of the upper is 24.5 inches and it weighs around 4 lbs.

Bottom Line

The PSA complete upper is a mid-length carbine ideal for hunting and self-defense. No other upper on the market can beat it on price. Especially with those extra BUIS.

Best Stripped for the Money:
 WMD Guns - AR-15/M16™ Nib-X Coated Upper Receiver


  • Easy to Install
  • Easy to Clean and Maintain
  • Exceptionally Low Jam Rate
  • Nib-X Coating for Smooth Cycling
  • Good for Firing Quick Successive Shots


  • Might Require Minor Fitting

This upper receiver from WMD guns features a Nib-X coating. The nickel boron coating is extremely wear resistant and reduces friction among parts to almost a negligible level. This coating protects the receiver from any damage and works extremely well with a bcg having a similar coating.

Plus it also makes the receiver easy to clean. A ceramic top coat has been applied on the exterior/exposed portion of the stripped receiver to improve aesthetics. The receiver features M4 feed ramps and is compatible with all mil-spec lower receivers. The receiver is compatible with 204 Ruger, .223 and 5.56 NATO calibers.

Respective of its Nib-X coating and tight tolerances, the stripped lower offers exceptional value for the money. The stripped upper receiver is ideal for competitions and long range shooting. Plus the coating on the receiver also reduces the overall cleaning efforts and sessions. The stripped upper receiver is not only aesthetically pleasing but also works well with all mil-spec lower receivers.

Bottom Line

The WMD stripped upper receiver’s Nib-X coating makes it exceptionally smooth and easy to clean. The upper works very well while shooting quick successive shots. Making it ideal for competitions and tactical applications

Best Side Charging Upper:
J P Enterprises - AR-15 PSC-11 Side Charge Kit


  • Ready for a Custom Build
  • Durable Full Mass Bolt Carrier
  • Features Side and Top Charging Capability
  • High Quality and Precision Cut Components
  • Cheekweld does not Have to be Lost when Charging the Rifle


  • Expensive
  • No M4 Feed Ramp
  • Can’t Use a Different Bolt Carrier

Side Charging Uppers are quite a rare sight with AR owners. Plus a side charging upper like this one is one of its kind on the market. The PSC-11 side charging upper from JP Enterprises is a dual charging receiver featuring both a top charging handle and a side charging mechanism.

Most side charging uppers compromise with features like the forward assist and rails, but this receiver features all of them. The upper receiver also features the JP full mass bolt carrier which has been precision machined from nickel chromium molybdenum steel.

The side charging handle can be removed for cleaning. Additionally, the upper receiver works any mil-spec standard lower receiver so there aren’t any compatibility issues.

The JP Enhanced bolt used in this upper assembly is exceptionally durable and will last for approximately 60,000 rounds. Side charging upper makes sure that you don’t have to take your eyes off the target while charging the weapon. This can be an advantage in certain hunting and tactical situations.

Bottom Line

Unlike most other side charging uppers, the PSC-11 doesn’t compromise on components. It even includes the top charging upper for convenience. The bolt carrier is proprietary since it has a notch which locks with the side charger.

However, you can replace the internal components of the bolts with standard mil-spec parts. The upper may seem a bit expensive, but its rarity and designs cover this issue.

Best 9mm AR Upper:
Foxtrot Mike Products - AR-15 9mm Upper Receiver M-LOK Assembled


  • Full-Length Rail
  • Ambidextrous Charging Handle
  • Button Rifled Barrel With 1:10 Twist
  • Ramped Bolt and Heavy Extended Upper
  • Durable Construction with Melonite Coated Finish


  • None

This upper from Foxtrot Mike Products has been specifically designed for 9mm caliber AR pistols. It is a complete upper receiver with a complete bolt carrier group. The upper has a 16-inch barrel featuring a twist rate of 1:10.

A couple of other barrel options in 10.5 inches and 8.5 inches are also available. The receiver has been manufactured using a premium Melonite-finish 4150 carbon steel, with the same finish on the bcg as well. The ambidextrous non-reciprocating forward charging handle is also convenient to use.

The barrel comes fitted with a compensator which greatly improves the value for money delivered by this upper receiver. A full-length rail runs all over the top of the upper receiver covering the handguard and the receiver. This gives you a lot of space to mount multiple optics at once. The FM upper receiver is compatible with most mil-spec lower receivers and is capable of cycling all kinds of ammo flawlessly.

Bottom Line

The FM AR-9 upper receiver is a complete package with the most durable and flawless components. The upper is ideal for building an AR 9mm pistol and is available in three different barrel lengths to choose from.

Best Left-Handed Upper:
Stag 15L Tactical Upper


  • Full-Length Rail
  • Left Handed Upper
  • 1:7 Barrel Twist Rate
  • Offers Customizability


  • None

The Stag 15L is a product from an extremely rare line of uppers for the AR-15. The upper has been designed for left-handed shooters and features the forward assist and charging handle on the left side. The upper features a 16 inch 1:7 twist chrome lined barrel and a 13.5-inch free float handguard.

The upper does not include the bcg or charging handle, so you get some space for customization of the rifle you are building. The upper features a full-length rail starting from the for-end of the handguard to the rear end of the receiver. Plus the M-Lok loops on the handguard also allow you to mount appropriate accessories.

Bottom Line

The Stag 15-L is a left-handed upper, useful for left-handed shooters. The upper is simple and allows you to customize the bcg and charging handle as you desire.

Best 300Blk Upper: 
Bear Creek 16" 300Blk Upper Receiver M-Lok


  • Excellent Value With Great Materials for the Price Point
  • Made and Tested in the USA and Backed by a Lifetime Warranty
  • 16" Parkerized 4150 Chrome Moly Vanadium Barrel with 1:7 Twist.
  • A Great All-in-One Solution for Budget Shoppers Who Want Quality
  • Contoured Barrel Profile, .300 Blackout Caliber, and Carbine Length Gas System


  • Not the Most Premium Upper Receiver on Our List, but Excellent for Budget Shoppers

The Bear Creek AR-15 16” 300Blk Upper Receiver is a complete upper assembly with a 16” M4 contour barrel profile made from 4150 chrome moly vanadium steel. This is very high-quality steel for this rifle’s price range. Additionally, it is given a parkerized finish to help maintain product quality for a long time to come. It also features a carbine length gas system and a 1:7 twist.

The assembly has a 15” M-Lok rail, an M4 flat top forged upper receiver, a charging handle, a bolt carrier group made to their own proprietary system standards, and a birdcage flash hider. This receiver is chambered in a .300 Black-Out and is machined with .300 blackout feed ramps in the barrel’s extension.

It should be compatible with most lower receivers, which is a good thing, because many gun owners will recognize Bear Creek as a quality brand. Their receivers have gained a reputation for great performance, and the materials used on this lower receiver are no exception to this rule. Expect to be able to burn through hundreds and hundreds of rounds without experiencing a jam or failure to fire.

We appreciate that Bear Creek, as always, commands a very reasonable price for their quality components. Often, gun owners looking for quality and value will wind up assembling everything piecemeal, but thanks to companies like Bear Creek, it is possible to get excellent performance in a package deal such as this.

Add Bear Creek’s lifetime warranty and the fact that all parts are handmade in the USA and passed through rigorous inspections prior to shipping, and you’ve got a real winner for anyone on a budget and shopping for a complete upper receiver.

Bottom Line 

Bear Creek produces excellent quality parts at reasonable prices, making this upper receiver a complete package of high-quality parts. Now you won’t have to put together an upper receiver from tons of individual parts unless you want to, thanks to Bear Creek.

11. Radical Firearms 10.5" 5.56 M4 Upper Assembly

We will note to start our last proposal with a notice that this upper receiver comes with a barrel less than 16" in length. This may require special licensing as a short-barrel rifle. Be sure to check state and federal laws to make sure your build is permissible.

The Radical Firearms 10.5" Barreled Upper assembly utilizes a carbine-length gas system and comes complete with an ejection Port Door, forward Assist, 10.5-inch M4 Profile barrel, barrel nut and A2 flash hider. The package doesn’t include Charging Handle and BCG (Bolt Carrier Group).

The shorter carbine gas system has a bit harsher recoil and the faster cycle rate. To provide reliable feeding both the upper receiver and barrel extension feature the factory-machined M4 feed ramps.

The Radical mil-spec Upper Receiver is an inexpensive, flattop drop-in solution for any budget.

While this is an excellent upper assembly for the price, Radical Firearms also brings some quality-control issues like loose set screws on the gas block or uneven coating on the upper.

Advantages of Investing in a Great Upper

Now as we have discussed the qualities of a good AR-15 upper, let’s take a look at some of the advantages of investing in one.


Investing in a good upper receiver for your rifle ensures reliability. A good forged upper receiver is quite durable and will withstand a lot of beating while being used for different purposes. A great upper receiver also has a longer lifespan, so you don’t have to replace it anytime soon.

Improved Accuracy

A good upper receiver with a decent barrel improves the overall accuracy of the AR-15 rifle. Barrels with good twist rates, pertaining to the caliber are helpful in upgrading the accuracy of the rifle.

Quick Caliber Switching

A specific caliber upper receiver allows you to change the caliber of your AR-15 almost instantly. Due to the simplistic design of the AR platform, all it takes is pushing in and out a couple of take-down pins to switch the upper receiver, and hence the caliber.


A complete upper receiver generally has all the necessary devices pre-installed. This includes the top rail, handguard, muzzle device, and sights. This ensures that you don’t have to search for these components separately. Additionally, the complete uppers are available at a more appropriate and economic price, as compared to individual components.


If you are concerned about the looks of your AR-15 rifle, investing in a cool looking upper receiver can solve your concern.

How to Clean an AR-15

Cleaning an AR-15 is relatively easy compared to other rifles. Mostly because of its simple design and mechanism. Before you start cleaning your AR, please ensure safety by cross-checking the chamber for the presence of any round. Both visually and manually. Once you are sure about safety, proceed further. The tools you’ll need are an Allen key, a flat head screwdriver, and an AR-15 cleaning kit.

Pull out the two take-down pins on the lower receiver to separate the upper receiver from the lower. Now keep the lower, and focus on cleaning the upper. Pull out the bcg and charging handle from the upper. Dismantle the bcg using an Allen key to pull out the firing pin and extractor. Clean these components with a rag and solvent, and lube them. Now use a bore brush to run dry and solvent soaked patches and a bore brush through the barrel. Remember not to pull the bore brush backward as it may damage the rifling of the barrel.

Once you are done with the upper receiver, shift your focus towards the lower. First, take out the buffer spring and clean them thoroughly with a rag. Now apply some cleaner and let it sit. You may disengage the trigger assembly and clean the lower receiver thoroughly using a rag and solvent. However, don’t try to disassemble the trigger housing group if you are not very sure about reassembling it. Just add some cleaning solvent, use ear swabs and get on with it.  

Apply small quantities of lube on all the moving/rotating parts of the rifle. But make sure not to overuse it. Now put the buffer spring back in place, and combine the upper with the lower using the two take-down pins.

For more detailed instructions on cleaning your AR-15, please refer to the video below.

How to Assemble an AR-15 Upper

Assembling an AR-15 receiver is concerned with a stripper receiver. Since a complete receiver is pre-assembled in as a drop-in part.

For assembling a stripped AR-15 upper, you have to collect all the important parts. These include the receiver, barrel, gas block, gas tube, handguard, bcg, charging handle and ejection port cover. The tools you’ll need are an Allen key, pliers, rubber mallet and a wrench.

The very first step is to install the ejection port cover to the receiver using a set of pliers. Once done, install the barrel to the front end of the receiver and lock it in place with the take-down pin, followed by tightening the barrel nut using a wrench.

Now install the gas block over the barrel and tighten the gas tube in place using the Allen key and the rubber mallet. Make sure to align the gas block with the index marking on the barrel so it sits in place. The next step is to install the handguard and lock it in place using the screws. If you have a muzzle device to be installed on the barrel, screw it on top of the muzzle and tighten it using the wrench.

Now push the charging handle in place and slide the bolt carrier group inside the receiver. That’s all, and you’re good to go.

For more detailed information and instructions, please refer to this video below.

Installation of an Upper Receiver

The AR-15's split personality enables even novices to install a complete upper receiver assembly upgrade on any standard-sized lower AR-15 receiver in a simple “plug and play” manner. That means you can connect a dedicated varmint or precision upper assembly or swap out different uppers chambered in a variety of calibers that will work correctly with standard 5.56x45mm lowers.

However, more experienced AR-15 owners may not be satisfied with this type of semi-industrialized customization. They may want to have a fully-customized upper assembly because it’s so key for accuracy, ergonomics, and overall weight.

As with most modification or repair jobs on AR platform rifles, the installation of an upper receiver just requires simple manual skills and only a couple tools.  

For any kind of modification, you should first have a vice to hold your receiver in place. You’ll need a basic toolbox that includes a light hammer and snap ring pliers. There’s also a couple custom tools needed, including a quality clamshell upper receiver action block, an armorer's wrench (necessary for installation and removal of any barrel), a torque wrench and a small brass punch to knock out the gas tube roll pin.

Common sense of course goes a long way. Give yourself enough time to do the job right and work in a well-lit work area. Since some pins and springs are small, it’s handy to have a tray to keep them in and a clear workspace in case they get away from you.

Here are the basic steps you should follow in assembling and installing your new upper receiver:

  1. After removing the factory upper from the rifle, you should take a new upper receiver, place it into the vice block and install the FA (forward assist) and ejection port cover.

The FA tooth should be oriented toward the receiver and fixed with the roll pin. The next step will be the installation of the ejection port via the spring and its rod.

However, if you bought an assembled receiver, you will be spared from these two activities, and you can start with barrel mounting.

2. The new barrel can be easily installed into the receiver with the help of the index pin on the barrel end that fits in a groove in the upper receiver. The barrel nut is screwed just like any other. It should be torqued with your armorer wrench until the next gas tube hole aligns correctly so you can insert the gas tube.  For this operation, you can use a torque wrench, adequately set to 35 in-lb. (or according to specific gas block instructions). It allows for better seating between the surfaces when installing the barrel nut.

The next step depends on your particular handguard, but only sequence of steps may be different in this procedure.

3. After properly attaching the barrel, the next level is to insert the gas tube in gas block or FSB (Front Sight Base). Fix it with a roll pin and slip the tube over the barrel and through the barrel nut. When you install the gas tube into the gas block, the side with a bigger hole is going to face down the gas block.

4. Next, slip your new handguard over the barrel and thread it all the way to the rear to align perfectly and flush with the back edge of the barrel nut. If you are using a drop-in handguard, you can simply side it on. These types can be installed with almost no tools, and they do not require the removal of the barrel nut or the front sight block.

5. Put on the muzzle device with its large ports looking toward the side of the barrel, so that the majority of the gases are vented to the side.

6. Stick the charging handle part way in the small channel slot and then slide it about an inch forward.

7. Take the bolt carrier group with the bolt placed in its most-outward position and align the gas key on top into the channel on the bottom of the charging handle. Push it into the receiver until it locks into place.

8. Place the complete upper receiver onto the lower receiver and push in the takedown and pivot pins to connect the two halves. That easily, you have a different gun.

It’s a saying that dates to the Wild West days, but it’s equally valid today: “Beware the man with only one gun; he probably knows how to use it”. It’s appropriately used for the knowledgeable AR-15 owner, who can easily convert his one gun to have multiple purposes. Since the AR-15 is customizable for any purpose and has more purpose-driven parts, many people are now buying specific upper receivers to add flexibility.


The upper receiver of an AR-15 is caliber specific and houses the bcg, charging handle, barrel, gas block and handguard of the rifle. An upper can either be complete or stripped. However, its quality depends upon its material and function. Investing in a good AR-15 upper helps with accuracy, reliability, and aesthetics of the rifle. Furthermore, assembling and installing the AR-15 is a simple and quick job with the right tools.

People Also Ask

Here we’ll answer some general queries associated with the AR-15 uppers. These are some common questions that arise in the minds of people and are helpful in tackling functional and legal implications.

How to Identify AR-15 Upper Manufacturer

The upper receiver manufacturer can be identified using the markings on the upper receiver. For example, AF is Alcoa Forge, PA is Capco/Anchor Harvey and so on. Below is a list of such markings and their respective manufacturers:

Upper Receiver Forge Markings

Offset Square is: Brass Aluminum Forging
LMT is No Forge Marks, but marked LMT or L is: LMT
AF is: Alcoa Forge
C AF is: Colt Alco Forge
A (splintered) = Anchor Harvey Aluminum
C MB is: Colt / Mueller Brass
Cardinal’s head (stylized bird head) is: Cardinal Forge
CH is: Colt Harvey Aluminum
Crosshairs w/"AR" is: ArmaLite
CK is: Colt / Kaiser Aluminum
CM is: Colt / Martin Marietta
D (stylized) is: Diemaco
DK is: Diemaco / Kaiser Aluminum
E is: Emco
EK is: EMCO/Kaiser
E MB is: EMCO/Mueller Brass
FA is: FNMI / Anchor Harvey
FK is: FNMI / Kaiser Aluminum
FM is: FN/Martin Marietta
FMB is: FNMI / Mueller Brass
LK is: LAR / Kaiser Aluminum
LM is: LAR / Martin Marietta
M "diamond" is: Mueller Industries
PA is: Capco / Anchor Harvey
PM is: Capco / Martin Marietta
Square (symbol) is: Brass Aluminum
M-16 markings:
CAF Colt / Alcoa Forge
CH Colt / Harvey Aluminum (1st Colt Forgings)
M Colt / Martin Marietta
DK Diemaco / Kaiser
FK, FS, BK, DK, EK, FK, AF, CW, AA, FS Bushmaster
LK FN / Kaiser
LM LAR / Martin Marietta (Army Spares Contract)
“Splintered A” F: FNMI Anchor Harvey“Splintered A” F: FNMI Anchor Harvey
“Splintered A” C: Colt Anchor Harvey
Splintered A Olympic Arms? (Anchor Harvey)

List of verified upper receiver forge markings used by AR-15 upper manufacturers/sellers

DSA - Cardinal forge
Rock River - Cardinal forge
Delton - Cerro forge, square
DPMS - Cerro
Spikes Tactical - Cerro
Stag - Cardinal, Cerro
LWRC- splintered A
Para USA - ZM
Knight’s Armament - Cerro (keyhole)
Wilson Combat - splintered A
Double Star - Cerro
Smith &Wesson - Cerro
Daniel Defense - Cerro
Sabre Defense - Cerro?
Remington - Cerro
BCM - Cerro, square
Bushmaster - Cerro
Stag - splintered A, Cardinal
J&T Distributing (Doublestar) - Cerro, C
CMMG - Cerro
Colt M4 - Cerro (C keyhole), square, Cardinal (“C“ bird‘s head), C AF

What Do I Need to Build an AR-15 Upper?

If you purchase a complete AR-15 upper, you’ll need nothing. But if you’re using a stripped receiver, you will need several components. These include bcg, charging handle, ejection port cover, gas block, gas tube, barrel, and handguard. All these components come with their respective pins and screws so you don’t have to worry about that. For the tools, all you’ll need is an allen key, a hex wrench, a set of pointed pliers and a rubber mallet.

How Long is an AR Upper?

An AR upper is approximately 7 inches in length. An AR upper fitted with a 16-inch barrel is approximately 24 inches in overall length. No matter what length barrel you use, you must take into consideration the legal implications of 16 inches rifle length.

Can You Put an AR Pistol Upper on a Rifle Lower

Yes. You can put an AR pistol upper on an AR rifle lower because the size of the pistol upper is the same as that of a normal upper. However, you still have to consider the length of the barrel. If the overall length of the rifle is below 16 inches, it will under the category of an SBR(Short Barrel Rifle) which has specific paperwork associated with it.

Michael Lutes

Michael Lutes is the managing editor and owner at Gun Mann. He is a veteran, gun enthusiast, 3 gun competitor, and 2a advocate. Mike has a passion for innovation and education across the industry to create great content, training, and insights from the best and brightest.

Leave a Comment