Building an AR-15: Ambidextrous Lower Receivers

AR-15 Ambidextrous Lower Receivers
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Building an AR-15: Ambidextrous Lower Receivers

Intro 101 - Building an AR-15

No rifle is more popular than the AR-15 and for several good reasons. It’s lightweight, customizable, and extremely fun to shoot. With so many firearm owners becoming familiar with its operation and how they work, building an AR-15 has become the latest trend.

Although this article focuses specifically on ambidextrous lower receivers, parts, and configurations, it's worth noting a couple of essential questions to ask yourself before you start your custom build.

First, you should ask yourself what the primary purpose of the rifle will be, this includes hunting, plinking, competition, and home defense.

Once you've decided on the primary use figuring out which type of lower receiver, upper receiver, and accessories you want will be much easier

Now that we have that information out of the way -
In the past few years, the rise of ambidextrous lower receivers on AR-15s has become much more prevalent.

While these lower receivers certainly benefit their southpaw owners, it was only recently that right-handed shooters discovered the hidden benefits of having an ambidextrous AR-15.

Classic AR-15 Lower Receiver Controls

The lower receiver portion of an AR-15 rifle is generally considered to be more than just a component, but rather the firearm itself (it's also the most legally regulated).

Components of a standard AR-15 consist of a magazine release button and safety selector switch, all located on the right side of the receiver. The left side has a little more going on, there’s a bolt catch/release that looks like a paddle above the trigger guard and a safety lever behind the trigger guard.

These controls, combined with the AR-15 charging handle, do everything necessary to keep the rifle fed with ammunition from the magazine.

Additionally, many AR15 owners claim that a good amount of "gun-juggling" is necessary when it comes to unloading or clearing malfunctions with this receiver layout.

After dropping the AR magazine, the right-hand moves from the pistol grip and pulls the charging handle back while the left hand engages the bolt catch.

This usually requires the rifle to be removed from the firing shoulder, taking a significant amount of time. *For a visual representation, view the AR15 Diagram photo below.

Complete AR-15 Diagram


Lower Receiver Housing
This is the main body or frame of the lower receiver. It is typically made of aluminum and houses various internal components.

Trigger Group
The trigger group includes the trigger, hammer, disconnector, and associated springs and pins. It is responsible for initiating the firing sequence when the trigger is pulled.

Pistol Grip
The pistol grip is attached to the lower receiver and provides a comfortable and ergonomic grip for the shooter. It typically houses the grip screw and may have storage compartments for small items.

Trigger Guard
The trigger guard surrounds the trigger and protects it from accidental activation. It can be either a standard trigger guard or an enlarged trigger guard for use with gloves.

Magazine Release Button
The magazine release button allows for the removal and insertion of magazines. It is typically located on the left side of the lower receiver and is pushed to release the magazine.

Bolt Catch
The bolt catch engages the bolt carrier group's bolt catch notch, locking the bolt carrier in the rearward position after the last round is fired. It is used to hold the bolt open for inspection or to facilitate magazine changes.

Safety Selector
The safety selector is a lever that allows the shooter to engage or disengage the firearm's safety. It typically has three positions: safe, semi-automatic, and sometimes a third position for automatic fire (on select-fire variants).

Buffer Tube Extension
The buffer tube extension, also known as the receiver extension, is attached to the rear of the lower receiver. It provides the housing for the buffer, buffer spring, and buttstock.

Buffer and Buffer Spring
The buffer and buffer spring work together to absorb recoil and help cycle the action. They are located inside the buffer tube extension.

The stock is attached to the buffer tube extension and provides a shoulder support for the shooter. It can be fixed, collapsible, or folding, depending on the desired configuration.

What is an Ambidextrous AR15?

Ambidextrous refers to the ability where a person can perform tasks and activities using either their left hand or their right hand interchangeably with equal skill.

An ambidextrous lower receiver (AR15) is designed to be easily operated by left or right-handed shooters.

It typically features controls, such as the safety selector, magazine release, bolt release, and charging handle, that either hand can easily access and manipulate.

In a traditional firearm, these controls are often optimized for right-handed shooters, making it less convenient or difficult for left-handed individuals to operate.

However, ambidextrous firearms are particularly beneficial in situations where multiple shooters with different handedness may need to handle the same firearm or in tactical scenarios where quick and efficient handling is crucial, regardless of the shooter's dominant hand.

Benefits of an AR-15 Ambidextrous Lower Receiver

In addition to the most obvious benefits for left-handed shooters, an ambidextrous lower receiver can streamline your ability to effectively manipulate your rifle when needed.

For example, when unloading or clearing a malfunction one of the more common mistakes is to slap a Magpul Battery Assist Device (BAD) on an AR-15 and call it a day.

The issue is it protrudes into the trigger guard and can be inadvertently activated through accidental contact. That’ll lock the bolt to the rear right in the middle of shooting the rifle.

Other advantages of an ambidextrous lower receiver include better control of the AR-15 when firing in a variety of "awkward" positions and decreasing the likelihood of getting brass ejected in your face - sounds like a win-win to me!

Pros and Cons of an Ambidextrous Lower AR-15 Receiver


  1. Left-Handed Compatibility: Ambidextrous AR-15s cater to left-handed shooters, providing them with equal ease of use and access to controls, enhancing overall shooting experience and comfort.
  2. Versatility: Ambidextrous controls on an AR-15 allow for more flexibility and adaptability in various shooting positions and scenarios, making it suitable for a wider range of shooters.
  3. Ambidextrous Charging Handle: An ambidextrous charging handle on an AR-15 enables convenient and efficient charging of the firearm, regardless of the shooter's dominant hand.
  4. Ambidextrous Safety Selector: With an ambidextrous safety selector, shooters can easily engage or disengage the safety from either side of the firearm, enhancing control and safety during operation.


  1. Increased Complexity: Ambidextrous AR-15s often have more parts and mechanisms compared to traditional AR-15s, which can potentially increase the complexity of the firearm. This complexity may lead to more maintenance requirements and potential points of failure.
  2. Cost: Ambidextrous AR-15s tend to be more expensive than their non-ambidextrous counterparts due to the additional design and manufacturing considerations.
  3. Learning Curve: Transitioning from a traditional AR-15 to an ambidextrous variant may require some adjustment and practice to become familiar with the different control placements and manipulations.
  4. Availability: Not all AR-15 models have ambidextrous variants or options, limiting the selection and availability of ambidextrous AR-15s in the market.

Two Popular Ambidextrous AR-15 Lower Receivers

The best way to gain a bunch of speed when clearing malfunctions is to shoot an AR-15 with ambidextrous controls that come from the factory.

The two best examples of what’s available today are from Lewis Machine and Tool (LMT) and Daniel Defense.

Lewis Machine and Tool MARS-L
The LMT MARS-L is an ambidextrous AR-15 that places an additional bolt catch/release on the right side of the lower receiver and a second magazine release on the left side.

The housing for the new bolt catch/release is part of the lower receiver forging, so it’s low-profile and out of the way, sitting just above the trigger on the right side.

This configuration allows the firing hand to stay on the pistol grip after dropping the magazine, while the left hand pulls the charging handle to the rear.

There is no faster way to lock an AR-15 bolt to the rear for malfunction clearance than this one. The second magazine release on the left side also has a fence around it that is integral to the receiver’s forging.

This means the rifle can be slung, muzzle down, and across the body without the risk of unintentionally dropping the magazine.

Lewis Machine Ambi Lower Receiver

Daniel Defense RIII Series
Daniel Defense has the new RIII rifles out, also featuring ambidextrous controls.

Daniel Defense did an equally excellent job as LMT and integrated the new controls into the lower receiver forging instead of just hanging a bunch of claptrap off the sides of the rifle. The DD4 Complete Ambi AR-15 Rifle Lower RIII features an enhanced flared magazine well, fully ambidextrous controls, and a rear receiver QD swivel attachment point. 

The RIII bolt catch/release is in the same spot, but the second magazine release sits a little lower and is still protected by a fence to prevent accidentally dropping the magazine.

Daniel Defense RIII Full Ambi - Complete Lower Receiver

Final Thoughts

While there are plenty of complete ambi rifles on the market - when and if you are building your own AR15, it's certainly nice to have options and ambidextrous AR-15's certainly work well for anyone desiring shooting practice off their support side.

However, clearing malfunctions and some types of reloads are substantially faster and more efficient with an ambidextrous AR-15, provided the controls are properly designed. LMT and Daniel Defense are the two best contemporary examples.

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