The most popular centerfire rifle in the United States today is the AR-15, and it has been for several years. It originally began with the M16A1 rifle. The AR-15 platform as we know it today, with all of its different variants and spare parts and accessories available on the market, can be linked back to the M16A1 from the late 1950s.

If you want to build together your own personal M16A1, the two most important components you will need are the lower receiver and the upper receiver. In this guide, we’ll dive into a history and overview of the M16A1 rifle, the purpose behind the upper receiver, a buyer’s guide, and a list of the best M16A1 uppers. Now, let’s start.

Best durable	WMD Guns AR-15/ M16 NiB-X Coated Upper Receiver	More durable than chrome plating Extended M4 feed ramps Options for different types of finish Needs additional parts (stripped receiver)	$99 Shop NowClick to read my review
Best budget-pick	Aero Precision AR-15/ M16 Stripped Upper Receiver	Comes with M4 feed ramps Compatible with most Mil-spec AR-15 lowers Affordable Takedown holes are a bit tight	$70 Shop NowClick to read my review
Best high-end	Sharps Bros Assembled Billet AR-15 Upper Receive	Compatible with many AR-15 cartridges Comes complete and ready to install right out of the box Mil-spec anodized finish Can’t be easily customized since it’s already assembled	$165 Shop NowClick to read my review
Top Pick	Wilson Combat AR-15 Billet Upper Receiver	Built for precision use for maximum accuracy potential Picatinny top rail for adding sights and accessories M4-style feed ramps ensure good reliability Not compatible with all aftermarket bolt releases	$215 Shop NowClick to read my review

An Overview of the M16A1 Rifle

The AR-15 as we know it today can be traced all the way back to the M16A1 from the late 1950s.

During World War II, the standard-issue rifle for the United States military was the M1 Garand rifle. It was an excellent rifle that was more technologically advanced than other nations’ bolt action services rifles during the war. However, by the 1950s, the M1 was showing its age as rifles with detachable box magazines such as the AK-47, FN FAL, and HK G3 began to equip the world’s other militaries.

The US military reacted by modifying the M1 Garand to shoot the .308 Winchester round. They began adding a detachable box magazine and shortening the gas tube. The result was the M14 rifle, or the M1A as its own in its semi-automatic only configuration for civilians.

While the M14 was a fine rifle, it also had its faults. I was too big and heavy. The hefty .308 round it fired was too big and heavy for jungle warfare in Vietnam.

So the military needed a smaller and lighter rifle that was more maneuverable that can fire an intermediate cartridge. The result was the M16A1, or the first major iteration of the AR-15 rifle (developed from the AR-10). The M16A1 is notably different from other M16 rifles for its triangular handguard, stock that lacks a compartment, and 20-inch barrel and rifle length gas system.

It originally lacked a forward assist and came equipped with a three-pronged flash suppressor and a parkerized finish very resistant to rust and corrosion. Parkerizing came standard as a finish on most American military weapons, including the M1 Garand and the Colt M1911A1 pistol, for this reason.

Later Developments of the M16A1 Rifle

The M16A1 was later developed into the XM16E1. It has a forward assist and notches in the bolt carrier produced from 1967 to 1982. Several other improvements were made to the M16A1 as well. For instance, the three-pronged flash hider originally present on it caught on twigs often, so the XM16E1 added an improved hider that mitigated this issue.

The M16A1 eventually paved the way for more M16 generations and its shorter cousin, the 16-inch barreled or shorter M4 carbine. While no longer in service with the American military, the M16A1 is still used by numerous other militaries worldwide, as the US government sold much of its existing M16A1 stockpile to other governments when new versions of the rifle were developed.

In essence, it really was the M16A1 that started it all when it came to the AR-15 platform. This is also why the M16A1 has seen a resurgence in the American market over the last few years. Companies like Brownells have sought to release their own versions of the M16A1 to appeal to buyers interested in a rifle with a much more classic look.

If you’re looking to put together your own M16A1, the upper receiver is one of the most important components you need to consider. Without a quality upper receiver, you won’t have a quality rifle.

Why Should You Upgrade Your Upper Receiver?

The upper receiver is the upper part of the AR-15. It includes the metal housing, barrel, handguard, ejection port, forward assist, rail system, bolt carrier group, etc.

Combining a complete upper receiver of an AR-15 with a complete lower receiver can create a fully functional rifle ready to go. The upper receiver is arguably the most important because it’s the part that impacts the shooting performance of your rifle the most. The biggest reason for buying an upper receiver is to improve your rifle’s performance.

For example, when you build a rifle with higher quality upper components, you can potentially boost the rifle’s performance by up to 50%. Furthermore, building your M16A1 with higher-grade components such as aircraft-grade 7075 aluminum will significantly improve its durability.

Buyer’s Guide to the Best M16A1 Upper Receivers

Complete vs. Stripped

When choosing any upper receiver, you will always need to choose between a stripped upper or a complete upper. It shouldn’t be hard to choose which one you should go with, depending on your objectives for your rifle.

A stripped upper receiver is an upper receiver that is not complete. You still need to acquire additional components and install yourself on the rifle. The components you need to get will vary depending on the upper you are considering.

On the other hand, a complete upper comes with all of the parts already installed, so it’s immediately ready to merge with a lower receiver (assuming that the lower is complete) to form a complete rifle. Since a complete upper receiver comes with everything installed already, more money will be out of the box. However, keep in mind that you’ll also need to spend the cash on the components you need to transform it into a complete upper.

To summarize, you should go with a complete upper if you don’t want to deal with any hassle or parts fitting. You should also go with a stripped upper if you’re going to customize your rifle to make it truly your own.

Material and Finish

The best upper receivers are built out of aircraft-grade 7075-T6 aluminum, which is lightweight and durable. It’s a far better choice than either polymer or 6061 aluminum.

Also, make sure that your upper comes with rust and wear-resistant finish, such as nitride or an anodized finish. This will ensure that your upper will hold up better in rough conditions or inclement weather.

Rail/ Mount

Your upper receiver should come with a rail over the top to make it easy to add lights, lasers, scopes, red dot sights, or other accessories. The M1913 style Picatinny rail is the best kind of rail to get. It will be compatible with many kinds of spare parts and components.

Forward Assist and Dust Cover

A dust cover is designed to keep grime out of the ejection port when the rifle is not used. The forward assist can help clear a jam if the round does not go all the way home. While neither the forward assist nor the dust cover is necessary to ensure proper function, both pieces are good to have, and ideally, your upper receiver will come with them.

If you go with a stripped upper that does not come with these components, at least make sure that it gives you the option to add them.

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The 4 Best M16A1 Upper Receivers for Your Rifle

Now that we’ve covered why you need to upgrade your upper receiver buyer’s guide, here’s our top list of the best M16A1 upper receivers:

WMD Guns AR-15/ M16 NiB-X Coated Upper Receiver: Best durable M16A1 upper receiver

WMD Guns is a company known for its high-quality finishes and coatings on firearms. This upper is no exception, coming with a NiB-X coating that is more durable than chrome plating designed to easily withstand 30,000 rounds. Specifically, the NiB-X includes nickel boron with durability greater than Melonite or Tennifer.

The body of this receiver is built out of aircraft-grade 7075-T6 aluminum and is available in a black, nickel, OD green, or flat dark earth color pattern. The extended M4 feed ramps ensure reliable feeding, but the takedown holes are also very tight and may require further fitting from a gunsmith. This upper is a solid option if you want an upper for your M16A1 that you know is built to last.

Aero Precision AR-15/ M16 Stripped Upper Receiver: Best affordable M16A1 upper receiver

Available for an affordable price point, this Aero Precision is a stripped upper receiver compatible with most mil-spec grade AR-15 lowers. It comes with quality M4 feed ramps to ensure consistent reliability and is built out of high-quality aircraft grade 7075 aluminum with a rugged coat Class 2 anodized finish. Aside from black, you can also get the Aero Precision in cerakote FDE or cerakote OD green.

The drilling holes may be a bit tight depending on the lower you’re going to match it, so installing it may require the aid of a gunsmith.

Overall, the Aero Precision Stripped Upper Receiver is a solid choice if you are looking for a stripped upper receiver ready for you to customize. Aero Precision designed this upper receiver to be compatible with most mil-spec 5.56 lowers, which is a great option for your M16A1 build.

Sharps Bros Assembled Billet AR-15 Upper Receiver: Best high-end M16A1 upper receiver.

This complete upper receiver is ready to install straight out of the box.You only need to add your handguard and a barrel, and it’s ready to go. It’s made of 7075 aluminum and is coated in a mil-spec anodized finish, so it’s very durable and rust-resistant. Also, it comes equipped with a forward assist and a dust cover.

The Sharps Bros. upper is compatible with multiple AR-15 calibers, including .224 Valkyrie, 6.5 Grendel, .300 Blackout, .223 Remington, and 5.56x45mm NATO receiver. However, due to the size of the ejection port, it cannot accommodate rounds such as .458 SOCOM or .450 Bushmaster.

This is the kind of receiver that you can use for a long time and pass on to the next generations.

Wilson Combat AR-15 Billet Upper Receiver: Overall best M16A1 upper receiver

The Wilson Combat AR-15 Billet Upper Receiver was built for precision use to ensure maximum accuracy potential. Wilson Combat also built this upper receiver from the ground up to address perceived design weaknesses from a structural Wilson Combat receiver. The company argues that this approach will help improve durability and tolerances.

This upper is made of aircraft-grade 7075 aluminum with a mil-spec grade black anodized finishing coating. It also comes equipped with M4-style feed ramps to ensure good reliability, an undersized bolt raceway to improve feeding and chambering, a Picatinny rail so you can add sights and optics, and a shell deflector.

The one negative about this receiver, besides its expense, is that it will not accept all aftermarket bolt releases. So to stay on the safe side, you should invest in Wilson Combat bolt releases instead.

Our Pick

Our top pick is the Wilson Combat AR-15 Billet Upper Receiver. It’s accurate and built for precision use. So, you can guarantee that it will improve your rifle’s performance. Plus, it will last a long time with its premium build

However, if the Wilson Combat Upper is out of your budget, then we recommend the Aero Precision AR-15/ M16 Stripped Upper Receiver. It’s durable and is a good upper for M16 builds. However, keep in mind that it’s a stripped one. So, you need to do a bit of research to find the other components you need to complete your rifle.

Wrap Up

Today, there are simply more parts available for an AR-15 in general than before. While this means that you have a plethora of different options for accessories, it also means it can more difficult to choose one.

We have provided you with the best M16A1 uppers receivers available today. Any one of the four upper receivers above will be an excellent option for your M16A1 build. Also, remember that you can always refer back to our buyer’s guide at any time when searching for a new upper receiver as well.

Which M16A1 upper receiver did you like the best? Let us know in the comments below.

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Featured image by u/DaddyDano