Best M4 Upper Receivers With Buying Guide

Why Invest in Great AR Uppers?

The M4-style modern sporting rifles are gaining more attention in the firearms industry today and so are its parts. If you are building your own M4-style rifle or just replacing the old upper, you will realise that there are many options available on the market for the M4 uppers.

The options of uppers can be overwhelming and lucky for you, we have narrowed it down to a list of the best M4 upper receivers on the market. However, before moving on to the list of best M4 upper receivers, we have prepared a guide to identify different uppers, the benefits of upgrading your M4 upper and the things to think about before you decide to buy one.

Are All M4 Uppers The Same?

Even though most uppers look the same, they are actually not. Some uppers are bare and basic, lacking certain components while others are complete with all the necessary components.

A complete M4 upper receiver will include a stripped upper receiver, forward assist, dust cover, bolt carrier group (BCG), charging handle, barrel, gas system, handguard and sights, optics or other accessories. A stripped one is generally just a piece of metal that houses all the components. However, there are some that include a forward assist and dust cover.

Although a forward assist is not as necessarily needed as compared to when it was first released, it is still great to have. Another difference between uppers is the way that they are built. Generally, the two common methods are forged or billet.

Forged uppers are usually a bit heavier but also tougher, but you won’t really be able to tell the difference between the weight of a billet and a forged one as they are very minimal. Lastly, you also have the option of a carry handle which can be used as a rear sight or a flattop which gives more versatility.

Benefits of Upgrading Your AR15 Upper Receiver

Getting a new upper for your modern sporting M4-style rifle can have quite a few benefits. First of all, old uppers will wear out as time passes by and you will start to experience poorer functionality and reliability. A new upper on the other hand gives you enhanced function and reliability. It can also improve your accuracy at a much lower cost than changing the rifle.

Sometimes there is a function that you might wish you have on your old upper. It could be a different style or rail length, a forward assist, better ergonomics or maybe a new caliber and with a new upper, you can get the function that was lacking. You might also want to get a few different uppers since the design of the M4 is extremely modular.

Usually, the uppers are exceptionally easy to switch out, allowing you to use different uppers in different situations. You might also want to change because of aesthetic reasons like its colors, finish and style.

Things to Consider Before Buying


The first thing that you should consider whenever you are buying components is their reliability. To ensure that you get the best option, you should go for uppers that are made by a trusted and well-known manufacturer. They will usually have a large customer base and you can judge the uppers based on their feedback and review.

Stripped or Complete

A stripped and a complete upper has a drastic difference in their price point, which is why it is important that you consider which is the right one for you before you buy. If you plan to pick every component on your own, then the stripped one will be highly suggested.

Material and Finish

Normally, the best M4 upper receivers are made of 7075 T6 aluminum with a mil-spec, hard coat finish. However, there are also some billet uppers on the market that are considered as a more aesthetic option than forged ones. There are also some that come with extra Teflon coatings or chrome-lining for better function and will usually last longer.

Best Rated M4 Upper Receivers

Now that you know the variations of the M4 upper receiver, the benefits of upgrading and the things to think about before acquiring, we can now move on to the 5 best M4 upper receivers on the market. Use the knowledge that you gained and pick the best one for your modern sporting M4 rifle.

1. Radical Firearms 16 in. 5.56


  • M-LOK rail
  • Assembled with forward and ejection port door
  • RF barrel nut
  • Anodized finish
  • 16″ barrel length


First on the list is a product by Radical Firearms. They are a manufacturer based in Texas that started small and made a name for themselves. What you will find with their products are nothing but quality and supported with a lifetime warranty just like this 16-inch M4 upper assembly.

This is perfect for any shooter of all levels that just wants a new complete receiver to go with their lower receiver without any hassle. The handguard system uses the company’s proprietary 12-inch FCR free-float rail and is able to give you great accuracy while keeping your hand away from the barrel heat.

The barrel that comes with it has a twist rate of 1 in 7 and is made of 4140 chrome moly vanadium with a melonite finish. It also has an A2 flash hider attached at the end. The receiver itself is an aluminum construction and has an anodized finish. In addition, the barrel nut is also a proprietary design that is easy to use.

You will fancy this if:

You are a fan of receivers with uniquely designed components. This receiver comes with multiple proprietary design components and if that’s what you want in your receiver, this would be a great choice for you.

You want something that is easy to install and use. This piece is great for anyone that is starting out or experienced as it is an easy drop-in installation.

You are searching for an affordable complete upper. For a complete receiver such as this, it is actually offered at a fairly low price range.

You will not fancy this if:

You expect consistent quality. The quality control of this complete receiver is not consistent so if you are expecting it to be perfect all the time, then this might not be the best option.

2. Bravo Company AR-15/M4 Complete Assembly


  • Mil-Std 1913 rail
  • Assembled with forward assist and ejection port cover
  • Precision machined from 7075-T6 aluminum
  • Laser etched T-markings
  • Type III, Class 2 hardcoat anodized finish


This piece is another professional-grade receiver by Bravo Company, a famous name in the modern sporting rifle industry. They are owned and operated by veterans and ex-special forces so they know how to develop the best weapons systems based on their experience in the field.

This upper is constructed to a military standard except for the barrel extension that is slightly smaller and unable to give a good fit for better accuracy. The top rail has laser etched T-markings to allow sights or other components to quickly and easily return to zero. This piece is also CNC-machined from a top-quality material to provide great strength to the overall construction.

A forward assist and an ejection port cover comes with the receiver. The forward assist includes a heat-treated, tool-steel pawl, featuring press fit and a pinned cap. A mil-spec dry film lubricant can also be found in the interior bore. This piece by Bravo Company is not exactly a complete upper but it does come with some of the components such as the forward assist and ejection port.

You will fancy this if:

You are looking for something with a top standard. This receiver is a professional-grade receiver built from top-standard materials and has the best design that will work for every shooter.

You enjoy the top rail with laser etched T-marks. The laser etched T-marks on the top rail are extremely great for helping sights or other components return to zero.

You don’t plan to spend too much money. For a top of the line receiver such as this, it is actually offered at a reasonable price range.

You will not fancy this if:

You prefer a great fit for the barrel mounting. The barrel extension is slightly undersized which won’t give a great fit.

3. Spikes Tactical Flattop


  • Standard M4 Picatinny rail
  • Comes with forward assist and ejection port door cover
  • Precision machined from 7075 T6 aluminum
  • Type III hardcoat anodized finish
  • Weighs 8.5 ounces


This M4 Flattop Upper is made by Spikes Tactical, a family-owned and operated company in Florida. Their products are all covered with a lifetime warranty so you don’t need to worry about their reliability. This model comes with two options, one with a forward assist and the other without. It allows you to choose whichever option that you need.

Due to the improvements made to the M4 design, a forward assist is not exactly necessary. Some shooters say it causes a jam while some say it’s useful. If you decide to go with the option that has a forward assist, the ejection port door will also be included.

If you are getting the model without a forward assist or ejection port door, it weighs 5.9 ounces only, but if you go for the model with a forward assist, it weighs 8.5 ounces. Either option will also have an impeccable fit and finish.

This M4 upper receiver is made from top of the line aluminum alloy and finished with a Type III hardcoat anodization. On top of that, you will also discover a standard Picatinny rail at the top of this M4 upper. The high-quality and top-standard build is the reason that it’s one of the best M4 upper receivers available on the market.

You will fancy this if:

You want to customize your own upper receiver. If you are building your own M4 rifle and plan to customize it to the way you prefer, then this would be the best choice as it offers room for customizations.

You want upper receivers with a high-quality build. Whether you go for the option with a forward assist or without, the construction quality will be consistent.

You will not fancy this if:

You prefer a complete upper. If you prefer to have a complete upper with all the necessary components such as the bolt carrier group and charging handle, then this would not be the best pick for you.

4. PSA 16″ Carbine Length 5.56 NATO 1:7 M4 Nitride M



  • Forged 7075 T6 aluminum
  • Magpul MOE handguard
  • Assembled with a charging handle and an M16 bolt carrier group
  • Finished with hardcoat anodizing
  • 4150V chrome moly steel barrel
  • Melonite barrel finish
  • F-Marked front sight base


This is a standard, 20th-Century-style upper made by PSA, a trusted retailer for guns and gun parts. It is a quick and easy selection if you plan to get something new. This is a complete upper which means it comes with all the necessary components like a barrel, charging handle and bolt carrier group.

The barrel is a high-quality piece built with 4150V chrome moly steel and is finished with a top of the line nitride coating. It has a 1 in 7 twist rate and with such a twist rate, it will be excellent for most bullet weights. On top of the 1 in 7 twist rate, the A2-style barrel includes a flash hider and has a F-marked front sight base.

The handguard is a classic A2-style design without any rail. A mid-length gas system is used for this PSA upper and the body has excellent strength because it’s forged. At the inside of this forged upper, there are M4 feed ramps and in addition to the M4 feed ramps, there is an M16 bolt carrier group.

The BCG has a parkerized exterior while the inside is chrome-lined for excellent reliability. The BCG is also made from a mil-spec, high-quality, shot-peened Carpenter 158 tool steel. If you are looking for a top-grade upper, this would be the best choice.

You will fancy this if:

You want to look for a high-grade and mil-spec upper. This upper is constructed with forged materials for excellent strength and durability so if that is what you are searching for, then this would be the best choice for you.

You are planning to look for a complete upper. This complete upper comes with all the necessary components such as a BCG and a barrel that comes with an A2 flash hider.

You will not fancy this if:

You prefer to have a rail to mount accessories. The handguard that comes with this complete upper doesn’t have a rail and without a rail, you lose the capability of mounting accessories that helps to boost your accuracy.

You expect a flawless quality control. Although it is a great piece, there are some issues regarding the quality control of their products.

5. Brownells – AR-15/M4 Stripped


  • Picatinny top rail
  • Precision machined from 7075 T6 metal
  • Finished with Type III hardcoat anodizing
  • Doesn’t come with forward assist or ejection port cover
  • M4 feed ramps


The last upper in this guide is a black, stripped upper receiver by Brownells. Brownells is probably the biggest and most well-known guns and gun parts distributor in the country so you don’t need to worry that their products are not good enough.

This Brownells upper is built to be mil-spec which means it will be compatible with most of the mil-spec parts available. With the use of a high-grade alloy to build this upper, its durability can be assured. On top of that, it is finished with a matte black, type III hardcoat anodized coating for aesthetic and longevity use.

This black upper by Brownells does not come with a forward assist or ejection port cover. Even though there is no forward assist or an ejection port door, it does come with feed ramps for reliable feeding. Plus, the top rail offers the capability of mounting accessories such as a sight.

You will fancy this if:

You prefer a good-quality mil-spec upper. This Brownells upper has the best quality thanks to how it’s constructed and finished which you will find to work best with your M4 rifle.

You enjoy customizing your own upper. If you prefer customizing your own gun and the upper too then this would be the best option as there is enough room for customizations.

You prefer having an upper that is offered at a lower price. Compared to the cost of others, this is considered as cheap and affordable.

You will not fancy this if:

You prefer a complete upper that comes with all the parts. This piece is not assembled with the parts that make up a complete upper.

Frequently Asked Questions (FAQ)

What are the best attachments for the M4A1?

Some examples of good attachments that work brilliantly with the M4 rifles are monolithic suppressor, stock M16 grenadier barrel, integral hybrid sights, 60 rounds magazine and a stippled rear grip tape.

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