What Is The Difference Between An Upper And Lower Receiver On Firearms?

The upper and lower receiver of a firearm is two of the most important pieces of the gun. And they each serve a unique purpose. 

  • The upper receiver holds the barrel, bolt, and other components of the gun
  • And the lower receiver contains the trigger, magazine, and other components. 

So, understanding the difference between the two can help you better understand the inner workings of a firearm. Today, I’ll discuss the differences between an upper and lower receiver on firearms and why they are important in my writing.

 

What Is A ‘Lower Receiver’ And Why It Is Dangerous?

A lower receiver is the part of a firearm that houses the trigger mechanism and the magazine well. It is the part of the firearm that is considered to be the firearm itself and requires a federal license to possess. 

  • Lower receivers are dangerous because they are the main component that allows a firearm to be fired.
  • They are also the only part of a gun that requires a background check and registration in some states.

Lower Receiver Classification: In Details 

A Lower Receiver is the part of a firearm that houses the trigger and firing mechanism and is the part that is legally considered a firearm, in the context of firearms. And it is required to be marked with a serial number. 

  • The lower receiver is generally made from aluminum alloy and is the frame onto which the stock, barrel, magazine, and other components are attached.

Lower receivers have several different classifications, depending on their design and intended use. The most common classifications are:

  1. Stripped Lower Receiver:  This is a lower receiver that has not been assembled with any other parts. It usually comes with the necessary holes for the stock, trigger guard, and pistol grip.
  2. Semi-Automatic Lower Receiver:  This type of lower receiver is designed to be used in semi-automatic firearms. It usually has a trigger assembly, magazine well, and other parts pre-installed.
  3. Fully-Automatic Lower Receiver:  The lower receiver is designed to be used in fully-automatic firearms. It usually has a selector switch, magazine well, and other parts pre-installed.
  4. Multi-Caliber Lower Receiver:  This type of lower receiver is designed to be used with multiple calibers of ammunition.

 

What Is An Upper Receiver And Its Ins & Outs?

An upper receiver is the part of an AR-15 rifle that houses the bolt carrier group, charging handle, and barrel. It is the top half of the rifle and is connected to the lower receiver by two pins. 

  • The upper receiver contains a variety of components, including the bolt carrier group, charging handle, barrel, gas system, handguard, dust cover, and forward assist. 
  • It also includes a variety of mounting points for optics, sights, lights, and other accessories.

 

What Is The Difference Between An Upper And Lower Receiver On Firearms?

  1.  The upper receiver is generally made from aluminum or steel. In contrast, the lower receiver is typically made from polymer or aluminum.
  2.  An upper receiver is the part of a firearm that houses the bolt carrier group- the charging handle, and the barrel. It also contains the gas system and the forward assist. On the contrary, a lower receiver is the part of a firearm that houses the trigger group, the magazine, the safety selector, and the pistol grip.
  3.  The upper receiver is what houses the majority of the firing mechanism. On the other hand, the lower receiver is the part that houses the magazine and holds the firearm together. The lower receiver is also the part that is considered to be the firearm itself. Therefore, it is the part that is regulated by the Bureau of Alcohol, Tobacco, Firearms, and Explosives. 
  4.  The upper receiver is generally interchangeable between firearms of the same caliber and manufacturer, while the lower receiver is not.

 

Is The Upper Or Lower Receiver Considered a Firearm?

The short answer is yes. The upper and lower receivers are both considered firearms as defined by the Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF). 

  • ATF Means: The ATF defines a firearm as “any weapon (including a starter gun) which is designed to or may readily be converted to expel a projectile by the action of an explosive.” This definition includes the upper and lower receivers of a gun, which are the two main components of the gun. 

Reasons:

  1. The upper receiver is the part of the gun that houses the bolt carrier group, barrel, and charging handle. And the lower receiver holds the trigger assembly, magazine well, and other components. These two components make up the majority of the gun together. Thus they are considered firearms in and of themselves. 
  2.  The other components of a gun such as a barrel, magazine, and trigger are also considered firearms by the ATF.

Note:

Any individual wishing to purchase or possess any of these components must do so in compliance with all applicable federal, state, and local laws.

And Is A Lower Receiver Considered A Rifle Or  A Pistol?

A lower receiver is the part of a firearm that houses the trigger, hammer, magazine, and other components that make up the firing mechanism. It does not determine whether the firearm is a rifle or a pistol. But that is determined by the upper receiver and barrel.

 

And What Is AR Lower? 

An AR lower is the frame of a semi-automatic rifle that’s built according to the dimensions and specifications of the AR-15. 

  • It is the part of the gun that houses the trigger and the magazine. 
  • It is usually made of aluminum or polymer and is the basis of all AR-15-style rifles.

 

Differences Between: An AR Pistol Lower And AR Rifle Lower

  1. An AR pistol lower does not have the same type of buttstock as an AR rifle lower. On the contrary, AR pistols are designed to be fired one-handed and are not designed to be shouldered like rifles.
  2. An AR pistol lower will typically have a shorter barrel than an AR rifle lower, usually between 4 and 12 inches.
  3. An AR pistol lower may have a different type of grips, such as a Magpul MOE K2+ or a SIG Sauer Pistol Stabilizing Brace They are designed for comfort and control when shooting with one hand.
  4. An AR pistol lower may require a special pistol buffer tube, while an AR rifle lower typically requires a standard rifle buffer tube.
  5. Due to its shorter barrel and lack of buttstock, an AR pistol lower typically has a shorter overall length than an AR rifle lower. 

 

Some Essential FAQs:

Can I Put A Pistol Brace On A Rifle Lower?

In most cases, no. Pistol braces are designed to be used exclusively on handguns. So that it can be used on certain rifle-style pistol receivers. But they are not designed to be used with full-length rifle receivers. 

  • If you are still unsure, please consult your local firearms laws or contact the manufacturer of the brace.

Can You Put A Stock On A Pistol Lower?

Yes, stock can be attached to a pistol lower. However, it is important to note that the pistol must remain a pistol and cannot be converted into a rifle. This means that any stock attached to the pistol must be an arm brace, not a stock.

An arm brace is designed to provide additional support and comfort when shooting the handgun. But it is not designed to be shouldered like a stock.

Is A Stripped Lower Considered A Rifle?

No, a stripped lowercase is not considered a rifle.

A stripped lower is the part of an AR-15 rifle that is the frame and does not include all of the necessary components (stock, barrel, or other action parts).

Can A Stripped Lower Be a Pistol Or Rifle?

Yes, you can put a pistol brace on a rifle lower. A pistol brace is an arm brace that is designed to provide extra support for a pistol or a short-barrel rifle when firing. 

  • It attaches to the back of the firearm. 
  • And it can be used to stabilize the firearm while firing.
  • A pistol brace can be used on any firearm with a buffer tube, including a rifle lower. 

However, it is important to remember that-

  1. A pistol brace may not be legal, and it may be considered a short-barrel rifle (SBR) under federal laws depending on the firearm.
  2. Therefore, it is mandatory to check the laws in your state and locality before using a pistol brace on a rifle lower.

 

Conclusion

The upper and lower receivers of a firearm are two distinct parts of the gun. The upper receiver houses the bolt carrier group, charging handle, and barrel, while the lower receiver contains the trigger group and magazine.

And when the two receivers are connected by the takedown pins, they are considered separate parts under the law. The upper and lower receivers together are responsible for the safe and reliable operation of the firearm.