Not many know this, but the AR-15 pistol is a handgun that derives its parts from the AR-15 rifle.
The AR pistol uses many identical parts to the rifle.
Examples of this are the lower parts kit, buffer system, bolt carrier group, and upper and lower receiver.
So what distinguishes the pistol from the rifle?
The answer is size.
AR-15 pistols, as expected, are typically smaller than their rifle counterparts.
The handguns employ shorter barrels. 7.5″ is the standard length for .223 or 5.56 cartridges.
In fact, an AR pistol in 9mm can be equipped with a barrel as short as 4”.
The Difference Between an AR Pistol Lower vs Rifle Lower
There is virtually no difference between an AR pistol lower and a rifle lower.
They only become different once a buffer assembly is added.
A buffer assembly usually consists of a buffer, spring, and receiver extension.
Once this is added the AR pistol lower cannot take a shoulder stock.
If you do so, the pistol turns into a short barrel rifle or SBR, and obtaining the appropriate license becomes mandatory.
Alternatives to Installing a Buffer Assembly
As an alternative, one can opt to use a “pistol” brace on the lower.
Such a brace looks like a stock, however is technically intended to hold onto the shooting hand forearm.
Many gun owners with this modification position the brace against their shoulder, akin to small stock.
Legally though this is kind of getting into murky territory.
The thing is, barrel lengths longer than 16” means a firearm is classified as a rifle.
As such, anyone can build the lower in any manner.
However, if the gun is shorter than 16” then it is a pistol, and handgun rules must apply.
The Legal Definition Governing the AR-15 Pistol
An AR-15 is considered a pistol if an AR-15 has a barrel shorter than 16”.
Such a pistol also should not have a stock. Its total length must be less than 26 inches overall.
The absence of a stock makes the AR classified as a pistol.
The moment you install any AR-15 platform regardless of caliber and even with a less than 16” length with a stock, it turns into a short-barreled rifle or SBR.
Needless to say, legal possession of a short-barrel rifle is allowed in most states.
To obtain one, the owner needs to undergo the NFA process, register the SBR, and comply with a $200 tax stamp fee.
Advantages of Having Your AR Classified as a Pistol
An AR platform gun classified as a pistol permits a barrel less than 16” and forgoes the NFA process.
There are some states, however, that do not allow the possession of short-barreled rifles despite the Federal law.
Due to this, the AR-15 pistol is the only choice for anyone that desires a short barrel AR-15.
While the regular AR pistol shoots rifle rounds from a rifle magazine, it is still considered a pistol based on the definition of the ATF.
Thus even if the AR performs like a rifle, the absence of stock, the short barrel, and overall length (less than 26”) qualify it as a pistol.
Building Your Own AR-15 Pistol
One starting from nothing will begin with an AR-15 lower, also called a lower receiver. Manufacturers of lower receivers have ceased labeling their receivers as either rifles or pistols.
Receivers are sold not particularly for a rifle or pistol.
Hence, one can buy any receiver and use it in a pistol configuration.
If one desires to use an 80% lower receiver, federal law also allows it.
To compare the process of putting together an AR pistol is usually very similar to building a rifle.
A few differences exist though.
For instance, one has to use an AR-15 pistol buffer tube assembly and/or an AR-15 pistol buffer tube.
It is vital to point out that a stock cannot be attached to a pistol buffer tube.
Should one assemble their own upper receiver, they will need to have a pistol-length gas system.
This is the essential difference between putting together a rifle and a pistol.
For those that want less of a hassle, there are many AR-15 pistol upper assemblies to choose from.
How to Keep Your AR Pistol Legally Compliant
If one is putting together an AR-15 pistol, one cannot modify a rifle to a pistol.
If one has a rifle and wants to convert it to a pistol, this is a no-no.
Conversely, if you have an AR pistol and later modify it to a rifle, and then back again to a pistol, this is legal.
It must be reiterated that adding stock is not allowed, but numerous alternative accessories to make shooting easier can be selected instead.
For instance, Thordsen cheek rest and proper sights are an alternative.
There is also the KAK Shockwave Blade Pistol Stabilizer or SIG SBX Pistol Stabilizing Brace that one can opt to utilize as a cheek rest or support the gun on the arm.
One is not allowed to shoulder any of these accessories, otherwise, the AR turns into a short-barreled rifle or SBR based on the ATF guidelines.