Why Is The Upper Receiver So Important?

The AR platform is relatively straight forward and offers ease in customization and modularity. Because of this, many people make the decision to build their own rifle or change and replace the upper receiver to change the caliber of the gun.

Completing your own build or swapping out AR15 upper receivers is achievable with the proper knowledge, tools, and product choices. Without, the process could go very wrong. It is a straightforward platform – not beginner simplistic.

AR15 upper receiver on gravel

The upper receiver you choose should be based on your individual needs. If you are going to be out in the elements often, you would want an upper that is more durable and able to handle that type of use.

Establishing your needs first will help steer you in the proper direction to make a choice. The next step is understanding the upper receiver and the options that are available.

The Function and purpose of an AR Upper Receiver

The upper receiver connects to the lower receiver and houses the charging handle, forward assist, ejection port, bolt carrier group, and a partial portion of the gas system. Combined, these components feed, extract, eject and even strike the primer of the rounds your gun fires.

These are crucial components, so it is important to take your time when you are making your choices. Always going for the least expensive may not be the best option, especially if you plan to depend on this rifle for home and self-defense.

Types of AR-15 Upper Receivers

Upper Receivers are either billet, forged, or casted. A billet receiver is constructed by milling a solid piece of metal to the proper shape from start to finish with a machining process. Forged receivers are created by forging (hammering) the upper into the proper shape and often utilizing machining to finish the process.

Casted receivers are made by pouring melted metal into a form, also known as die casting, and then finished with some machining. Forged receivers tend to be more dense and heavier, often considered the most durable. Billet and casted receivers are less dense and generally lighter.

Billet AR upper receiver on concrete

Upper receivers are made from various metals, but aluminum is by far the most popular. Your choice should be determined by what your individual needs require.

Going beyond construction, upper receivers generally come in two forms known as “carry handle” or “flat top”. A carry handle upper receiver has a fixed carry handle also houses the rear sight. A flat top upper receiver is the most common or popular as it has a picatinny rail on top. I typically recommend the flat top upper receiver as it is much more versatile for the end user and also more widely available.

Upper receivers are also referred to as A1, A2, A3, and A4. Simply defined, the A1, A2, and A3 upper receivers have a permanent carry handle, thus making them carry handle receivers. The A4 does not which makes it a flat top upper receiver and is the only upper that can utilize an optic without needing an adapter.

The Forward Assist Reality

The forward assist is a largely debated topic as to whether or not it is needed for civilian rifles. This is a stock feature on most AR’s and is also automatically included on many upper receivers. The purpose of the forward assist is to ensure that the bolt is securely in place. When you push the forward assist, the plunger moves forward and engages the bolt carrier group moving the unit forward making certain the bolt is seated firmly after chambering a round.

Most people believe this to be an antiquated device as it originated with the M16A1. This gun could possibly jam if it were running dry or dirty, which was common in military conditions at that time. The ability to manually put the gun into battery was thought to be crucial, and the forward assist served that purpose. However, not everyone agreed on its execution.

Most notably, Eugene Stoner once stated that the AR15’s forward assist could cause more issues than solve. The military disagreed, and so our standard issue M4 and M16 rifles still feature the forward assist to this day.

Incorporating the forward assist is a personal preference. If you do tend to lean towards keeping the forward assist, there are many upgrades available that give it a more contemporary look and design.

Handguards Are an Important Aspect of Your AR15 Upper Receiver

Just like the AR platform itself, handguards are extremely modular. They come in varying shapes, sizes, colors, and styles. They also go by various names such as forend or forearm – all meaning the same thing, handguard. The handguard literally does what the name suggests, it guards and protects your hand from the heat generated by shooting.

Some things to consider when it comes to choosing a handguard would be mounting options, weight, accuracy, heat resistance and ease of installation. Some are very easy to install, while others require you to modify your AR.

Two types of AR-15 build with different handguards

The handguard surrounds the barrel and allows you to hold and support the rifle with your support side hand. Most handguards are polymer or aluminum and are designed to help keep the rifle lightweight.

Free float handguards are a great example of this as they may require you to disassemble your rifle to complete the install. It is very important to do your research prior to purchasing to ensure that the product you are getting matches your gun-smithing abilities.

Rounding Out Home and Self-Defense Options

When it comes to upper receivers for home defense purposes the common calibers used are .223 REM, 5.56 NATO and 300 Blackout Subsonic ammunition.

The 300 Blackout Subsonic is becoming very popular in recent times as it is a heavier weight and considered to cause greater impact. It is also a lower velocity than a 5.56 or .223 equivalent which some say helps alleviate over-penetration.

A must have in my own opinion for your upper receiver would be a reliable optic and back-up sights. A reliable optic that you take the time to train with and make certain is zeroed properly for you, will give you a tremendous advantage in accuracy and faster sight acquisition. Technology with optics has come a very long way in a short amount of time, and they just keep getting better. Features such as shake-awake and automatic turn-off are beneficial to ensure battery life.

Another feature that is starting to trend is the addition of night vision capabilities within certain optics. This is a great feature in low-light conditions as it spares you from having to utilize your flashlight which could essentially give away your position. Of course, you would also need night vision goggles, which can range anywhere from 1,800 dollars to 10,000 or more.

AR-15 built for home defense

Barrel length is another factor to take into consideration when it comes to home and self-defense.

The most common barrel length in the AR platform is 16”. This length can be a little much when it comes to maneuvering throughout your home with a rifle. Some people opt for 10.5”. 11.5” and 12.5”, however a rifle right around 14.5” is actually a great option because you can pin and weld a muzzle device without having to go through the NFA process. This length will still allow you to maneuver around walls and doorways and can also go from home to vehicle and storage with ease.

Even though optics are growing exponentially in their technology, I still urge everyone to incorporate co-witnessed back-up sights. Many people state that this is antiquated thinking, however… technology, no matter how great always possesses the possibility of failing at some point. Having back-up sights that are co-witnessed with your optic is a solid contingency plan should your optic ever fail you.

Choosing the right upper receiver for your rifle is far more thought driven than most would think. With the proper research and truly evaluating your individual needs and desires, building an AR, or just swapping out your upper receiver, can be a very enjoyable experience.