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.

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