Blueprint to Building an AR-15

AR15 is one of the most popular models of rifle on the market. According to Fox Business, over 30,000 AR’s were sold during a seven-day period at a single store. Though the reason for a purchase can range from a simple competition firearm to trying to beat gun bans, it is obviously that it is one of the most popular models. Due to its aesthetic design and its similarity to the military’s M4, those who are not familiar with firearms have allowed ignorance and fear to dictate their political agenda.

This has resulted in bans like the California state law that prohibits the sale of Assault Weapons within state borders. Other areas have restricted access at the behest of President Obama. Despite this, only 48% of people support stricter gun control. Despite many of these unpopular restrictions, many states do not prohibit the manufacturing of firearms even if the limit the sale. With the development of CNC technology, it has become possible for an individual to create all the parts of an AR in their garage.

Aftermarket & CNC Design

In order to build your own custom AR, you have two major strategies in which you can approach the build. The first is to focus on purchasing all of the items from the appropriate manufacturers. This allows you have company that can provide refunds as well as help you troubleshoot their products. Generally, commercial AR parts are tested and have a higher standard of quality. Despite these benefits, there is a drawback.

Photo Credit: Wikimedia Commons

If you want to buy a lower receiver from a commercial manufacturer, you will have to go through the same process as buying a pre-built firearm. This is because the lower receiver is the only piece on an AR that bares the weapon’s serial number. Buy purchasing a commercially manufactured lower receiver, you are essentially purchasing an entire rifle in the eyes of the government. That said, you will have the ability to sell your weapon to another party in the same way that you could sell any other rifle.

The second option is to use a personal CNC machine to create your own parts. Most commonly this is used as a way to bypass the restrictions placed on the lower receiver. While it is possible to to make a lower receiver from scratch, it is easier to buy an, “80% complete” lower receiver for as little as $60.00. 80% means that the lower receiver has sections that have not been cut out and does not render this part operational in its present condition. Because it falls under the ATF’s threshold as a firearm, you do not have to deal with the restrictions placed on firearms.

Once you have an 80% lower receiver, a personal CNC machine can be used to cut out the needed sections and make this part fully operational. This results in a firearm that does not have a serial number and is completely unregistered. Due to the fact that you made it, it is legal to own, but will be illegal to sell to any other person. If you are interested in building AR’s as a business, you will need an FFL license to sell to the public. The process can be confusing, so check out our guide to make the process easier.


Before we discuss the parts needed for an AR, it is important to discuss the common variants in the civilian market. The primary purpose of your rifle should factor into the components that you build it with. Below are three of the major categories and each part will have a recommended part for each.


Competition AR’s are built for shooting on a range and controlled situations. Rather than outfitting your rifle with several tactical accessories to increase the appeal of its appearance, competition AR’s use the highest quality materials to increase accuracy and effectiveness. For pre-built competition AR’s Rock River Arms is one the industries leaders. Their LAR-15 R3 retails for around $1,400.00.


Some people believe an AR-15 is an ineffective weapon when it comes to hunting. In comparison to more traditional hunting rifles like a 30-06 Springfield, it uses a smaller round, has a lower velocity, and smaller muzzle energy. For larger game like deer, an AR15 toes the line of being enough to get the job done.

This is because the round isn’t designed to kill larger animals but rather to wound them. It stems from NATO’s need to find a universal combat round in order to simplify logistics concerning combat. NATO believes that a wounded combatant will inhibit others from fighting because they will stop to take care of their comrade. If the wounded combatant dies, then it frees the others to return to the fight. Due to this reason, the AR-15’s standard 5.56mm round is not ideal for hunting large game.

This does not mean it isn’t effective for all forms of hunting. For many, the AR-15 is a leader when it comes to hunting coyotes and foxes. These smaller animals are often harder to hit and the semi-automatic nature of the rifle allows hunters to quickly engage their targets while the magazine capacity allows shooters to have enough rounds to finish the job.


For many, a budget AR is one of the first experiences one uses to begin custom builds. This can be due to limited financial resources or because you want to experiment creating your own through a CNC machine without making a large investment. If you want to build a budget AR, the best way is to purchase each piece individually as it can save a significant amount of money when compared to the MSRP of brand name weapon. Remember, if you plan to use an 80% lower, it is illegal to sell it without a serial number. This is only a good option if you plan to keep the rifle for personal use.

Parts List

Upper Receiver

Budget: $279.99

Hunting: $639.99 (With BCG)

Competition: $679.99 (With BCG)

The upper receiver is the portion that holds the bolt, barrel, sights, gas chamber, and pretty much everything that comes in direct contact with the round. The upper receiver will determine exactly what round your AR chambers. It is important that the elements of upper receiver are manufactured with optimum quality because they have the largest impact on the actual performance of the weapon.

Poor quality barrels can have a rifling ratio which reduces the maximum effective range of the round. In addition, if the materials are compromised, this can create a potentially fatal situation if the weapon malfunctions during operation. Though it is possible to create portions of the upper receiver with a CNC machine, it is highly advised that you use tested uppers from established manufacturers. The above video shows an example of a catastrophic malfunction caused by a squib round.

Bolt Carrier Group

Budget: $99.97

Hunting: $159.59

Competition: $263.31

The bolt carrier group has several small pieces and has a multitude of purposes. The bolt carrier group is responsible for cycling an AR through the stages of firing. These pieces have a direct result on the reliability of your AR. If you have a faulty extractor pin, your weapon may experiences a large number of malfunctions as it makes it hard to eject the round. The same problem can occur if your firing pin is failing to strike a cartridge’s primer.

It is possible to purchase an entire kit for your bolt carrier group, but if you want to buy each piece individually, you will need:

    Firing pin


    Bolt Carrier

    Retaining Pin


Lower Receiver

Budget: $39.99

Hunting: $395.00

Competition: $405.00

The lower receiver is the focal point of an AR because all of the other elements attach to it, and it is the only piece that carries the serial number. Once completed, the lower receiver will bare the trigger, stock, selector switch, and magazine well. Due to being the piece that acts as the interface between the user and the weapon, it is important to pay attention to personal comfort and preference when it comes to building your lower receiver.

Trigger well

Budget: $25.99

Hunting: $240.00

Competition: $269.00

The trigger setup is a bit complicated to install, though still doable with some patience and a bit of instruction. One factor that is useful in considering is the weight required in the trigger pull. The competition grade trigger assemblies allow adjustable sensitivity. Small trigger pulls help with a shooter’s trigger squeeze, but they can also make the rifle prone to negligent discharges, so the hunting focused trigger assemblies have set weights at three, four, and five pounds of pressure.



Budget: $35.00

Hunting: $170.40

Competition: $246.36

Iron sights are not always used on AR’s though they do offer a great backup for those who need to have reliability in extreme situations. If you plan on using your AR for competition or varmint hunting, it is wise to purchase flip up sights as they can be adjusted so they are not in the way of your primary system. For a budget AR, fixed sights can provide a solid platform to engage targets. Some of the older AR-styles have fixed sights built into the upper receiver.


Budget: $49.99

Hunting: $459.00

Competition: $678.00

Reflex sights are commonly known as red dot sights, though not all use a red dot. They are built on quick, two-eye open style which keeps the shooter aware of the world around them. In addition, reflex sights are great for engaging close range targets since you only need to place the reticle on the target. Reflex sights can range from around $50 to a couple hundred, so make sure to research each one instead of assuming each is equal.


Budget: $91.49

Hunting: $189.99

Competition: $232.63

Scopes offer a magnification over standard vision. Many inexperienced shooters think that this is needed to shoot easier, though low quality scopes can turn a great weapon into something unreliable. Since most AR’s have a max effective range around 500 meters, it isn’t necessary to use a long range scope designed for a high-powered bolt-action rifle. A popular brand that is between a full powered scope and reflex sight is the ACOG. It offers enough magnification to aid in shots out in the 300 meter range, but not enough that it tunnels the weapon in and makes it ineffective at close range.


Building an AR can save money and offer the freedom that many experienced shooters want when it comes to their weapon. If you decide to create a custom AR, you may consider selling. In order to abide by federal regulations, it is necessary to obtain an FFL in order to sell your brand’s personal weapons directly to a consumer. If you need help navigating the process, check out our FFL Guide. Thanks for reading, and we hope you are having an awesome day

Brandon Maddox :