What is the best AR-15 lower receiver? Expanding on my last article about what to look for in an AR-15 upper receiver, lower receivers are the next major component we need to look at. When it comes to finding a quality lower, one of the most inane and misunderstood arguments that presents itself online is that “there are only three forges, and you are just paying for a roll mark.”
Quite frankly, this argument is played out and has been debunked repeatedly…however it does still rear its ugly head. As such, let’s go ahead and put it to bed once and for all.
Yes, there are only three forges that make lower receiver blanks. That has no bearing on why one company’s receivers are consistently made well, while others have such grievous errors it is laughable. When a company gets a receiver blank, or the manufacturer who is doing the OEM work gets them, from there it is up to the machinist to do things properly. A quality machinist is worth their weight in gold, but every company SHOULD have quality control and quality assurance in place to make sure that the human error element is eliminated.
Unfortunately, this is where many brands fall short. They are saving money somewhere, and one of the most common places this money is shaved off is in the QA/QC department. On some low priced parts, batch testing is common. This means some things will slip through the cracks, for the end-user to discover. Often these companies will have “amazing warranties” that seem too good to pass up. The sad reality is, that warranty is as flawed as their parts, as they are using customers for quality control. When you warranty a faulty part, you are just rolling the dice again, hoping what they send you is properly done and in spec.
When you are buying a lower, you need to understand what it is responsible for, and what the common points of mistakes are. The lower receiver is responsible for holding the fire-control group. One of the more common issues you will find on assembled lowers is the use of weaker springs which leads to light strikes on rounds. Also, it is common in batch tested brands to have fire-control group pockets that are not milled to the correct width. This prevents the trigger from moving freely and can prevent the hammer from rotating (if they can fit in the pocket at all).
The lower is also responsible for attaching to the upper receiver and the receiver extension. Attaching to the upper receivers is done via two pins. If the holes for the pins are not drilled correctly, or are not even, keeping the receivers attached can prove challenging.
The receiver extension threads on to the rear portion of the lower receiver houses some small parts such as the buffer retainer spring and detent and the safety detent and spring. While the buffer detent and spring are not part of the cycle of operations, if the hole where they live is not properly drilled, breaking your gun apart to work on it can be difficult. Improper placement can also lead to issues with attaching the receiver extension, as it will require either too much or too little threading. This will have a direct impact on the buffer system and its performance.
Now that we have discussed the basic functions of the lower and common places to look for in terms of errors, there are A LOT of brands that put out great quality receivers at various price points. Some companies will offer stripped lowers, a receiver with no other components installed. Others will offer complete lowers in either a rifle or pistol configuration. These will typically have everything installed already, including a fire-control group and a receiver extension with either a stock or brace.
Also, like the upper receivers, lowers can be either forged or billet. Forged lower receivers are chunks of metal heated up and hammered into a rough shape before machining. This changes the molecular structure of the metal, making it a stronger material. Billet lowers, on the other hand, are pieces of raw stock that are completely machined to shape without taking a beating. These will usually have a trigger guard as part of the machining and are often slightly fancier looking.
Aero Precision makes my list again, putting out a consistently good lower receiver. Offering both stripped and complete lowers, Aero’s receivers are generally the starting point for quality in terms of budget-friendly options. I will say with Aero, I do tend to lean towards their stripped receivers. Aero frequently offers builder sets and monthly specials that are a good way to add interesting color combos and roll marks to a gun without a giant price increase. Ambidextrous versions are available as well.
Sons of Liberty Gun Works crank out some incredible quality receivers for the price point. Parts are going to fit properly, each item is individually inspected, and options include stripped or complete with a ton of components available. Sons of Liberty Gun Works also offer a variety of roll marks that change not only the logo but also the selector markings. There is even an option for custom Cerakote and graphics on your receiver set if you wish. These are worth looking at for a duty grade rifle. Sons of Liberty also offers what is most likely the largest amount of customization with their small parts, if you elect to go for a complete lower.
With William Larson praising their work prior his passing, it is difficult not to give Sionics a hard look when considering lower receivers. Available in a complete or a semi-stripped (includes everything but the fire control group and buffer assembly), these receivers are ready for hard use. Sionics is another company putting a great quality duty lower that will not leave you wanting in the end. There is an option for an upgraded complete with ambi controls if needed.
BCM is another great duty grade option for lowers. Unless you are shopping for cosmetic blems or buying used, BCM only sells completed lowers on their site. These will be available in several configurations and will include some great lower components. These are great options for the price point and will hold up under hard use.
VLTOR produces some incredible lowers, all of which are slightly different than a standard receiver. The Vulcan line, (their cosmetic blems) are available in either stripped or complete configurations, but sell out quickly. Normal receivers are only sold as completes with standard receiver extensions, pistol setups, or with the VLTOR A5 system in place. Regardless of which receiver you get, they will include an oversized mag release button and a 3-position QD endplate (even on the Vulcan stripped receivers).
Arguably the hardest receivers to find in today’s commercial market, the Hodge lowers demand a premium and are worth it to their devoted customers. These items are impeccably machined, hold exacting tolerances, and usually sell out within minutes of a shipment dropping. If you plan on hunting down Hodge receivers, make sure you have a steady internet connection or you might just miss out. You can learn more about Hodge in this recent article from ARBuildJunkie.
LMT offers a few different options for receivers. Their basic, the Defender, is a high-quality lower receiver without any bells and whistles, just quality parts. If you step up to the MARS lower, you have access to one of the best AR-15 lower receivers that’s ambidextrous on the market today. Even as a stripped receiver, the MARS comes equipped with ambidextrous controls that are as much a part of the receiver as the machined aspects. Defenders and MARS are available stripped or complete in a few different configurations, including PDWs.
KAC components are legendary in the industry, and their lower receivers are no different, and are some of the best AR-15 lower receivers available. They can be purchased commercially as completed, ambidextrous lowers, you will only find the highest quality parts installed. You can find stripped receivers that are ambidextrous or standard, and these are just begging to be turned into a hard use firearm. Be prepared though, as Knights receivers demand a premium above almost all others, but there is a reason they have remained one of the most reputable companies in the industry.
These fully ambidextrous lowers are rock solid and well designed. Billet 7075-T6 construction with user-friendly controls already installed, the only things missing are the fire-control group, grip, and buffer components. If you are a fan of billet receivers, you’ll be hard-pressed to find one that is more thought out and comfortable to use.
Lower receivers are a critical part of any build. While I included a few companies here, there are many more that put out a great receiver. Figure out the purpose of your gun, what your budget is, and what perks you require, and you’ll be on your way. If you are looking for an ambidextrous receiver, there are options out there for you. Want to have a functional gun that will leave your Instagram followers drooling? Find a lower that will let you flex on them.
In the end, only you can determine what you consider to be the quality level you find acceptable. Just make sure you do your research and make sure the company isn’t using you as its line of quality control.
Todd Gimian is a gunsmith based out of Las Vegas, Nevada. After receiving his degree from Sonoran Desert Institute, Todd has spent his time building and maintaining a variety of machine guns and product testing for various companies. His main focus is expanding his knowledge on the AR-15 platform and helping bring better quality products to the market for end-users to enjoy.
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