So, you wish to build your own AR-15 upper receiver? This article aims to make it as quick and painless as possible for you.

The article will discuss why each individual part was selected and which tools are really needed for a successful build. It will then go through two (2) different builds that should cover the major differences in gas blocks, barrel, and handguard installations.

This guide will go through the various types of AR 15 upper receivers.

Different Types of AR-15 Uppers Receivers

Your receiver will be either a flat top or a carry handle. A flat top has a picatinny rail on the top of the upper, while carry handle uppers feature a fixed carry handle on the top of the upper. Note that the carry handle is essentially a rear sight assembly, so you probably should not use it to carry your weapon.

You will often pick up news of receivers as being A1, A2, A3, or A4 receivers. There have been a number of articles that explains this in detail, but generally the only big difference is flat top vs carry handle. The other big reflection is the forward assist button. Some uppers have them, some do not.

It is arguable whether this button is really needed for non-combatant use, but just remember all military M16 and M4 rifles have them for a reason – a tap on the forward assist will guarantee that the bolt is fully seated.

So which upper is the best fit for you? It is recommended to use a flat top upper with a forward assist for most setups – the picatinny rail provides adaptability, and it is the most popular style of upper, which means that it is (generally) affordable and plentiful.

Forged Upper Receivers

Forged metal uppers offer the ideal grain structure or orientation that yields the best mix of mechanical properties like hardness, fatigue limit, specific weight and a few others but they are denser and heavier. A forged upper is created by forging (hammering) the upper into the proper form and then typically it’s finished up with a CNC lathe.

Billet Upper Receivers

The billet receiver is completed by milling a solid hunk of metal with a CNC, until it is the proper shape. Billet metal has comparable mechanical properties to forged, however they are less dense and lighter at the expenditure of a little strength in the material.

Cast Upper Receivers

Cast metal is the lightweight of the group, but it also offers the least amount of strength. But since it’s usually the lightest upper, sometimes cast is “good enough”. Cast uppers are made by pouring melted metal into a form (also known as “die casting”). Typically, some finish work is then done with a CNC.

Stripped vs Complete Uppers

A stripped upper contains of only the upper receiver itself – it is basically just the main solid piece of metal. A completed upper will come with the ejection port door and the forward assist button fitted. You will also see complete upper assemblies, which usually include the complete upper along with the charging handle, barrel, handguard, and possibly the bolt carrier group.

So basically, the stripped lower is generally a single part – the upper receiver. A complete upper will come with a few more parts. And a complete upper assembly is a full upper-half of an AR15 rifle – just attach to a lower receiver and it is ready to operate.

Summary

This may seems like it is a lot of information – It generally is. When purchasing your first AR15, you need to know what to look for and then decide what is best for your needs. Buy yourself a rifle which meets recognisable standards of quality. If a manufacturer does not advertise the mil-spec feature set, then they probably do not stick to it. 

What if you have already bought brand X? Not a problem. As long as it works properly it will probably give you many years of good use. If something breaks, you just have to replace it with quality mil-spec components. If you take Brand X to a carbine class, you better take on spare parts. We hope this buyer’s guide is a helpful introduction to America’s rifle: the AR15.

If you are looking for more thorough information about any one component, search a few forums. We hope we have helped you get your ‘feet wet’.