Understanding How AR15 Uppers Work and Why You Need One

The AR-15 upper. Most of them work in similar fashion to each other and I guess that is obvious. The AR-15 upper, in this case, refers to the upper portion of the AR-15 which houses the barrel and gas system, as well as the bolt and rail system. They are the most easily interchangeable portions of the AR-15 because they do not carry any serial numbers. n upper contains

  1. a charging handle,
  2. delta ring assembly
  3. gas tube
  4. gas block
  5. dust cover
  6. hand guard
  7. Barrel
  8. flash hider
  9. and forward assist.

While there is a basic setup for all AR-15 uppers that are composed of the parts above, there are  a few variations in which many AR-15 owners  choose to customize their AR-15s.

The Style of AR-15 uppers

There are 4 distinct versions of the AR-15 upper receiver that people can take advantage of, whether going for a more high performance build or a more classic AR style look.

A1 and A2. Those who prefer a more classic look to their ARs go for these because they both feature the  AR-15 carry handle. These usually require an optic that is lifted or one that is attached to the barrel if the hand guard is also on that more classic design.

The Flat top uppers, or the A3 and A4 uppers are practically built to house whatever accessories you want. Although many would advise against strapping a single build with all the fixings, in favor of a more specialized build, the possibilities are nearly endless with these two upper receivers.

The Forward Assist

The forward assist’s purpose in modern civilian rifles has been the topic of a lot of debate, as it is essentially a tool designed for situations where a complete field strip can’t be done. In combat situations, the forward assist is a valuable asset, as if dirt and debris clog the action, the forward assist allows the user to manually push the bolt forward and chamber another round. This usually  helps clear up the  debris in the action, allowing the AR to be fired as normal. However, for those who think it is a useless addition, some uppers come without it.

Charging handle

The charging handle is used to pull the bolt back in order to chamber the first round. After that, it is all up to the gas system to cycle the action.

The charging handle is one of the more useful tools on an AR-15. However many would agree that the stock charging handle on an AR-15 is not a specialized piece in any way. Fortunately the aftermarket is home to many different variations of the charging handle that make it much easier to rack that action.

T Marks

The T marks on an upper receiver are made for measuring locations on the upper in order to more efficiently mount accessories. They are called T marks because the markings are at the top of the upper receiver on the picatinny rail.

Delta Ring Assembly

This area of the AR-15 is very important, as it is the location in which the barrel is connected to the upper. Not only that, but the handguard, which is meant to protect the hand from heat and provide extra mounting capabilities for optics relies on a securely built upper. This part of the upper is composed of the:

  • delta ring
  • barrel nut
  • weld spring
  • barrel snap ring


The AR-15 is made completely of metal and polymer. And while metallurgy and polymer manufacturing have definitely come a long way since the AR-15 was first designed, such a combination doesn’t insulate against heat very well, especially when there is nothing between the hand and the barrel. That is where the handguard comes in. Its sole purpose is to be held  by the user and protect against the heat created by constant firing. Handguards were primarily made in polymer, however, with the grade of polymer back then, and even to this day, they cannot be useful for protecting against heat as well as securely holding whatever accessories you want. It’s just too much to ask for the material.

And while Aluminum is able to do both to an extent, aluminum is still a metal, and is naturally a conductor of heat. There are handguards which make use of the metallurgical and polymer advancements to create more insulated handguards in the aftermarket.

Gas tube

The gas tube is responsible for sending a portion of the gas that has expanded inside the barrel back to the bolt, which provides enough energy to cycle the next round. In this way, the AR-15 is a gas powered firearm, different from other systems which use the blowback, or a piston in order to cycle the next round.

Never cheap out on the components of a gas system as they are the only thing making the gun a semi automatic action.

Flash hider

The flash hider screws onto the muzzle of the barrel, which should be threaded already. Its purpose, especially on ARs that have shorter barrel lengths than the standard 16” is to hide the flash of the muzzle. A round that is fired is also pushing out the remains of gunpowder that has yet to be burnt up and not all of the powder burns up inside of the barrel, creating the muzzle flash that we all know and hate. The flash hider reduces the flash an AR might create which makes it a must have battle implementation, especially on night time excursions. Understanding how the AR-15 operates is very important. This knowledge will help you to define the standard an AR-15 upper should be achieving, and therefore help you raise the bar on your own personal build when it comes to customize and optimize.

How to build an AR-15 pistol?

The AR-15 is a great platform for many reasons. It is a modular platform, allowing for many different attachments to be installed on it. Optics, grips, stocks and much more can be bought in the aftermarket to personalize and maximize the efficiency of your AR-15 build. They are largely accessible on the internet as many different companies supply AR-15 parts and kits to make for easier building. You don’t have to buy an AR-15 in one piece. Because many of the pieces are interchangeable, you can buy whole kits or an array of parts that people have for sale online. Not only is it easily accessible online, but it’s also one of the cheapest rifles to get, making it a first choice for many new gun owners.

It is a great entry level firearm because of the relatively cheap and recoil friendly ammunition it uses. However, this carbine rifle also comes in fun size, if 24” of lightly constructed aluminum and polymer were just a little big for your tastes. The AR-15 pistol, seen on the same spectrum as any handgun you might own, is what you are looking for. However, there are some legal constraints you should know about before getting into one. So here is how to build an AR-15 pistol legally.

What is not legal ?

The AR-15 is great because its platform is able to ride the line of rifle or pistol pretty freely except for a few criteria that would label it as an AOW. AOW is an acronym for the legal term “Any Other Weapon,” meaning any other weapon that is not considered a rifle, pistol or shotgun, pursuant of the National Firearms Act of 1934. In this act, the legal definitions, and therefore criteria for what constitutes a rifle, pistol, shotgun and SBR are made clear. Exceeding or not meeting these criteria could land you in the slammer for quite some time if you don’t have the appropriate tax stamp for your AOW. 

How long can your barrel be?

The first and easiest step to building an AR-15 pistol is the barrel. This also entails the gas system which I will also talk about. The barrel length must be shorter than 16” and getting even shorter than that will help you avoid any nefarious eyes that might get the ATF called on you. The barrel is the essential part of this  setup because it directly affects the overall length of the AR-15.

As a disclaimer, you should know that the AR-15 is not designed for a barrel length under 16”. Because of this, the gas system and the barrel will both wear out in about half the amount of shots it might take on a regular sized barrel. Take that worth a grain of salt though, as many different factors can influence barrel and gas system health. A good tip for maximizing the use on your AR-15 pistol would be to use ammo with a lighter load, and to not use the stock gas system you might get from the kit you buy. Especially if you buy an upper that is already assembled, they generally come out overgassed and this is not something you want if the health of your gas system matters to you.

Recoil is not  necessarily an issue with the AR-15 pistol, because the .223 rem and the 5.56×45 NATO are very light rounds already. The frame is heavy enough, and your buffer also helps dissipate a lot of the recoil even the more of the energy is coming out. And do us all a favor: USE A FLASH HIDER.

No stock on an AR-15 pistol?

 A pistol cannot have a stock. It also can’t have an adjustable stock or adjustable apparatus that aids in shouldering the gun as guns with stocks are meant to be shouldered. While there have been some iffy letters on the subject of shouldering an AR-15 pistol, the consensus from the ATF is that it is completely legal to shoulder a pistol.

So what can you use if you can’t use stock? Fins and braces are the best and while they are not technically stocks, you can shoulder them with some degree of comfort. The SBA 3 brace is one of the more popular braces out there. It was originally designed for use by amputees to be able to securely hold the firearm when firing with one hand. It was pretty immediately popularized as its construction helped keep a more tactical appearance on peoples shortened AR-15s without having to pay for a $600 tax stamp.

What attachments can’t you have on an AR-15 pistol?

The AR-15 is prized for its ability to accept many different attachments on  many different mounting systems. However, if you go the route of building an AR-15 pistol, certain attachments will not be available to you.  Vertical Forward grips are illegal to attach to your AR-15 pistol as such an attachment will classify the firearm as an AOW which requires a tax stamp in order to legally own. C grips and angled fore grips are completely fine as they aid in stability of the firearm, because let’s be honest, we know we aren’t actually firing the weight equivalent of a common handgun.

No Modifying what’s already built

The last thing that you cannot do in order to build an AR-15 pistol  is modify an already manufactured firearm. Ergo, you cannot take your AR-15 rifle you bought, disassemble, buy a new barrel, slap it on and call it day. That kind of stuff requires a manufacturers license, something gun buyers aren’t just carrying around. If you are going to build an AR-15 pistol,  play it safe and purchase the  correct parts from trusted companies online.

While you might think there are a lot of restrictions on the AR-15 pistol, that is because there are. But that doesn’t mean there aren’t other things you are capable of doing with them. Since they are legally defined as handguns, they are concealable on your person or in your car with  a concealed weapons permit.

AR-15 pistols are great for close quarters self defense situations. They are smaller and ultimately lighter than their carbine rifle counterparts. If you are looking for a quality AR-15 look no further than  for all your AR pistol needs.

Guide To AR-15 Upper Receivers

The AR-15 itself is made up of a few systems that all come together in the end to deliver an accurate shot that can cycle quickly and efficiently. The buffer assembly is responsible for mitigating recoil as well as providing the spring force necessary for the bolt to recycle ammunition from the magazine. The gas system is responsible for sending gas from the fired cartridge from the barrel back to the gas key on top of the bolt so that the recycling process can happen which entails the ejection of the spent cartridge and the addition of a new one. The trigger obviously is responsible for firing the ammunition.

Almost all of these require one important part in order to function, and that is the upper receiver. The upper receiver does a majority of the work when it comes to firing and cycling the action over the lower receiver. The lower receiver is really only meant to house the trigger group and the magwell and that’s about it. But why is the upper receiver such a heavy lifter? Why is there even an upper receiver in the first place? In this article we will go over the intricacies of the upper receiver, and what you can do to help your upper perform much better.

The upper receiver is quite possibly the most important part of the AR-15 as a whole. That is because, where the lower is meant really just to fire the ammunition, the upper receiver houses many of the components that directly affect the performance of the AR-15. That is especially since it contains the barrel, the gas system and the bolt, 3 of the main things that can severely affect your ARs performance whether good or bad.

What is the barrel of an AR-15?

The barrel of an AR-15 is actually made in two parts, and is one of the more stressful parts of the AR-15 to produce in high quantities. That is because manufacturers must be sure that the level of pressure the barrels are able to take meets the quality standard. Anything less could end a shooter up in the hospital or worse. The chamber is what connects to the AR-15 upper receiver, where the headspace must be near perfect in order to ensure a safe shot.

The AR-15 Gas System

The gas system of the AR-15 is a little more complex than the other parts and that is because of the sheer amount of calibers the AR-15 is able to take. Contrary to popular belief, it is actually a myth that an AR-15 gas system is a “one-size-fits-all.” The standard AR-15 gas system is really meant for either .223/ 5.56 NATO, although even then the pressure on a 5.56 NATO is a little higher than what you would want on your gas system.

The type of gas system you are using on your AR-15 build is important because it can directly affect the longevity of the other systems in the AR. That being the bolt and gas system itself, as well as the health of the bore over time. The buffer assembly can also suffer greatly. When there is too much gas entering the system, it is called overgassed. A good way to witness this happening is by looking at the round as it is ejecting. If the ejected cartridge is thrown out and behind you then that means the cartridge is overgassed. If the ejected cartridge is thrown out and in front of you, that means the system is undergassed. In this case, the buffer spring is able to start closing before the cartridge is able to fully eject, which springs the casing forward. A perfectly balanced system will eject the casing outward, perpendicularly to the orientation of the AR-15. However, this is something many AR-15 owners like to manipulate as you don’t need to swap out gas tubes, keys, or blocks in order to get this done. In this case, the parts of the buffer; the buffer spring and buffer weights can be changed to produce a different effect. When manipulating the gas system, you directly affect the longevity of the build, but that’s a given with most every modification you can make that isn’t simply adding furniture. The performance of your AR-15 for you is the most important part of owning your own AR-15.

Why switch out bolts?

Bolt carrier groups come in all shapes and sizes. The AR-15 bolt is a special one as it comes in a variety of different finishes. There are nickel-boron, phosphate, and nitride. Nickel boron and chrome lined bolts are the best of the bunch, but come at a much higher price. This is because they smoothen up the action, have anti-carbon build up properties even without using oil (always use gun oil) and generally have  a much nicer aesthetic appeal. Because of its anti carbon build up properties, maintenance  is much easier. Do NOT take that for an excuse to not clean your AR-15.

Nitride and phosphate barrels do not provide as much resistance to carbon build up, but can still offer a good amount of longevity if the gas key is chrome lined. This helps reduce wear and tear on the gas system as a whole, and helps fight against carbon build up in the gas key.

Bolts can still provide some aesthetic value to your AR-15 build as many companies offer different finishes to their bolts. Check those out here.

Conclusion The AR-15 upper receiver houses many of the AR-15’s core components. This means that you can modify the different parts of the upper to yield either an enhanced performance or a choppy one. Either way, knowing the functions of the AR-15 upper is key in modifying your AR-15 in the way you want it to perform.