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Build an AR-15 – An Introduction

At AR15discounts.com, we’ve helped countless enthusiasts answer the question of how to build an AR-15. This guide aims to provide newcomers with a comprehensive overview of the AR-15 building process, focusing on part selection, general knowledge, and the proper mindset needed to approach this endeavor. While we won’t be providing step-by-step assembly instructions, this information will help you understand the complexities and considerations involved in creating your own AR-15 rifle.

Our focus will be on building a reliable, general-purpose AR-15 suitable for a wide range of applications. For most builders who want to build an AR-15 rifle, we recommend a 16″ barrel with a mid-length gas system, paired with a quality trigger, barrel, and bolt carrier group. This configuration offers an excellent balance of reliability, accuracy, and versatility.

Build an AR-15 – Understanding the AR-15 Platform

The AR-15 rifle is a modular rifle system, which means it’s composed of various interchangeable parts. This modularity is both a blessing and a challenge for first-time builders as they attempt to build an AR-15. It offers incredible customization options but can also be overwhelming due to the sheer number of choices available.

The Anatomy of an AR-15 Rifle

At its core, an AR-15 rifle consists of two main assemblies:

1. The Upper Receiver Group
2. The Lower Receiver Group

Each of these assemblies is made up of several components, which we’ll explore in detail throughout this guide.

Build an AR-15 – Choosing Your Parts

As experts in the AR-15 market, we at AR15discounts.com have seen trends come and go. However, some principles remain constant when it comes to building a reliable, general-purpose AR-15. Let’s dive into the key components:

1. Lower Receiver

The lower receiver is the foundation of your AR-15 build. It’s the serialized part that’s legally considered the “firearm.” When selecting a lower receiver to build an AR-15, consider the following:

• Material: Most lower receivers are made from aluminum, with 7075-T6 aluminum being the most common and durable option. Some manufacturers offer polymer lowers, which are lighter but generally considered less durable for long-term use.
• Finish: Anodized finishes are standard and provide good corrosion resistance. Cerakote is another popular option that offers excellent durability and comes in various colors.
• Features: Some lowers come with enhanced features like ambidextrous controls, flared magwells for easier magazine insertion, or tension screws to reduce play between the upper and lower receivers. While these can be nice, they’re not necessary for a first build.
• Manufacturing process: Forged lowers are the most common and typically the strongest. Billet lowers allow for more complex designs but are usually more expensive. For a first build, a quality forged lower is more than sufficient.
• Brand reputation and quality: Stick with reputable manufacturers known for consistent quality control. Some well-regarded brands include Aero Precision, Bravo Company Manufacturing (BCM), Dirty Bird Industries, and Daniel Defense.

Remember, the lower receiver sets the tone for your entire build. It’s worth investing in a quality component from a reputable manufacturer, as it will be with you for the long haul.

2. Upper Receiver

The upper receiver houses the bolt carrier group and attaches to the barrel. It’s a crucial component that affects the overall reliability and accuracy of your rifle. Key considerations include:

• Material and construction: Like lower receivers, uppers are typically made from 7075-T6 aluminum. Forged uppers are the most common and offer excellent strength and durability. Billet uppers allow for more intricate designs but are generally more expensive.
• Compatibility: Ensure your upper receiver is compatible with your chosen handguard system. Some handguards require specific upper receiver designs or barrel nuts.
• Features: Consider whether you want a forward assist and dust cover. While not strictly necessary, these features can be helpful in certain situations and are standard on most mil-spec uppers.
• Finish: Anodized finishes are standard and provide good corrosion resistance. Ensure the finish matches or complements your lower receiver for a cohesive look.
• Feed ramps: M4 feed ramps, which are slightly extended and wider than standard feed ramps, can enhance feeding reliability with a variety of ammunition types.

For a general-purpose AR-15 rifle build, a quality forged upper receiver with M4 feed ramps, a forward assist, and a dust cover is a solid choice. Brands like Aero Precision, Dirty Bird, BCM, and Daniel Defense offer excellent options that will serve you well.

If you’re feeling overwhelmed about where to begin with your upper receiver, AR15Discounts has streamlined the process for you. Their user-friendly app simplifies the configuration of your .223/5.56 Complete Upper, allowing you to customize it to your exact specifications.

The app comes pre-loaded with sensible default options, making it accessible even for beginners. To use it, simply navigate through each step, clicking to make your selections from the available choices. The intuitive interface guides you through the entire process, from barrel selection to muzzle device. Once you’ve fine-tuned every detail to your liking, you can easily add your custom-configured upper receiver to your cart with a single click, making the entire experience hassle-free and efficient.

A Note on AR-15 Rifle Combo Upper and Lower Reciever Sets

Combo upper and lower receiver sets provide a convenient option for AR-15 builders. These matched pairs ensure perfect fitment, eliminating compatibility issues. Typically made from quality aluminum, they offer a reliable foundation for rifles. Available in various finishes and designs, from mil-spec to enhanced models, these sets streamline building an AR-15 rifle and often save money. They also guarantee consistent aesthetics for a cohesive look.

3. Barrel

The barrel is the heart of your AR-15 and significantly impacts its performance, accuracy, and overall handling. For a versatile, general-purpose AR-15, we recommend a 16″ barrel with a mid-length gas system. Here’s why, along with other important considerations:

• Length: A 16″ AR-15 rifle barrel offers a good balance between maneuverability and ballistic performance. It’s also the minimum length for a rifle without requiring NFA (National Firearms Act) registration. The mid-length gas system on a 16″ barrel provides smoother cycling and potentially increased reliability compared to a carbine-length system.
• Caliber: For beginners, we strongly recommend starting with 5.56 NATO/.223 Remington. This caliber is widely available, relatively inexpensive for practice, and offers good performance for a variety of applications. Your barrel should be marked as 5.56 NATO to safely handle both 5.56 and .223 ammunition.
• Profile: AR-15 rifle barrel profiles affect weight distribution and heat dissipation. A medium contour or government profile offers a good balance for general use. Heavier profiles can aid in heat management during high-volume shooting but add weight to the front of the rifle.
• Material and finish: Chrome-lined barrels offer excellent corrosion resistance and longevity, making them a good choice for general use. Nitrided (sometimes called Melonited or QPQ) barrels offer similar benefits and potentially better accuracy. For a first build, either option from a reputable manufacturer will serve you well.
• Twist rate: This refers to how quickly the rifling in the barrel makes one complete rotation. For versatility with various bullet weights, a 1:7 or 1:8 twist rate is recommended for 5.56 NATO.

Quality barrels are available from manufacturers like Faxon, LMT, Ballistic Advantage, and BCM. Remember, the barrel is not the place to cut corners – a good barrel is crucial for accuracy and reliability.

4. Handguard

TheAR-15 rifle handguard serves multiple purposes: it protects your hand from barrel heat, provides a platform for accessory mounting, and can contribute to the overall accuracy of the rifle. For a general-purpose AR-15, consider the following:

• Length: Choose a handguard that’s slightly shorter than your barrel length. For a 16″ barrel, a 13″ to 15″ handguard is ideal, providing ample space for a comfortable grip and accessory mounting while allowing for proper muzzle device clearance.
• Mounting system: Free-float handguards are highly recommended for their potential accuracy benefits. They attach directly to the upper receiver and don’t contact the barrel, reducing the potential for point-of-impact shifts due to pressure on the handguard.
• Material: Aluminum handguards offer an excellent balance of strength, heat dissipation, and weight. While polymer options are available and can be lighter, aluminum is generally preferred for its durability and rigidity.
• Attachment system: M-LOK has become the industry standard for accessory attachment, offering a sleek profile and wide compatibility. KeyMod is another option but has become less common. Avoid older quad-rail systems unless you have a specific need for them, as they’re heavier and less comfortable to hold.
• Weight: Consider the weight of the handguard, as it affects the overall balance of the rifle. Skeletonized or lightweight designs can help reduce front-end weight without sacrificing functionality.
• Heat management: Look for handguards with good ventilation to help dissipate barrel heat during extended shooting sessions.

Reputable AR-15 rifle handguard manufacturers include BCM, Hodge Defense, Midwest Industries, Dirty Bird, and Aero Precision. A quality free-float M-LOK handguard will provide a solid foundation for your build and allow for future customization as your needs evolve.

5. Bolt Carrier Group (BCG)

The Bolt Carrier Group (BCG) is the heart of your AR-15’s operating system. It’s responsible for chambering rounds, firing, extracting, and ejecting spent casings. A reliable BCG is crucial for the overall function of your rifle. Here’s what to consider:

• Material: The bolt and carrier should be made from high-quality steel. Carpenter 158 steel is the mil-spec standard for the bolt, known for its durability and resistance to premature fracturing. 9310 steel is another excellent option that some manufacturers use. For the carrier, 8620 steel is commonly used and provides good durability.
• Finish: A properly applied finish enhances corrosion resistance and lubricity. Phosphate is the mil-spec standard and provides a matte grey appearance. It’s durable and holds lubrication well, though it can be slightly harder to clean. Nitride (or QPQ) offers excellent corrosion resistance and lubricity, and is easier to clean. Nickel Boron and similar coatings provide enhanced lubricity and ease of cleaning but may be more expensive.
• Full-auto vs. semi-auto profile: Full-auto profile carriers (often marked “F/A”) are heavier and can provide smoother cycling. They’re completely legal in semi-auto rifles and are generally preferred for their reliability benefits.
• Staking: Ensure the gas key is properly staked to the carrier. This prevents the screws from backing out during operation, which can cause malfunctions.
• Testing and inspection: Look for BCGs that have been properly tested and inspected. MPI (Magnetic Particle Inspected) and HPT (High Pressure Tested) markings indicate the bolt has undergone these quality control measures.
• Extractor and ejector: These components should be made of durable materials and have strong springs to ensure reliable extraction and ejection.

For a general-purpose AR-15 rifle build focused on reliability, consider BCGs from reputable manufacturers like BCM, SOLGW, Toolcraft, or Microbest. A phosphate or nitride finished, full-auto profile BCG that’s been properly tested and inspected will serve you well in most situations.

6. Trigger Group

The trigger is your interface with the rifle and can significantly affect your shooting experience and accuracy potential. For a general-purpose AR-15 rifle, you want a trigger that balances reliability, safety, and performance. Here are some considerations:

• Mil-spec vs. aftermarket: Mil-spec triggers are known for their reliability but often have a gritty feel and heavy pull weight. Quality aftermarket triggers can offer improved feel and performance while maintaining reliability.
• Single-stage vs. two-stage: Single-stage triggers have a continuous pull until the break. Two-stage triggers have a light first stage followed by a heavier second stage. Two-stage triggers are often preferred for precision shooting, while single-stage can be faster for close-range work.
• Pull weight: For a general-purpose rifle, a pull weight between 4-6 pounds is a good balance between safety and performance. Lighter pulls can enhance precision but may not be suitable for high-stress situations.
• Reset: A short, positive reset can help with rapid follow-up shots. However, ensure the reset isn’t so light that it could lead to accidental double-taps.

For a first build focused on reliability, a quality mil-spec trigger or an enhanced mil-spec trigger (like the BCM PNT or ALG ACT) is a good starting point. If you decide to upgrade, reputable options include the Dirty Bird 2-stage, Geissele SSA, LaRue MBT-2S, or the ALG QMS. These offer improved performance while maintaining the reliability needed for a general-purpose rifle.

7. Buffer System

The AR-15 rifle buffer system plays a crucial role in managing recoil and ensuring proper cycling of your AR-15. It consists of the buffer tube (receiver extension), buffer spring, and buffer weight. For a general-purpose 16″ mid-length AR-15 rifle build, here’s what you should consider:

• Buffer tube: Stick with a mil-spec diameter carbine buffer tube. These are widely compatible with stocks and offer proven reliability. Some enhanced buffer tubes feature improved finishes or minor tweaks like drainage holes, but a standard mil-spec tube is sufficient for most builds.
• Buffer spring: A standard carbine spring is suitable for most builds. Some manufacturers offer enhanced springs (like Springco or Tubb’s flatwire springs) that can provide smoother cycling and increased longevity, but these are usually unnecessary for a first build.
• Buffer weight: For a 16″ mid-length gas system, a standard carbine buffer (3 oz) or H1 buffer (3.8 oz) typically works well. The H1 can sometimes provide smoother cycling, especially if your rifle is slightly overgassed. Avoid heavier buffers unless you’re experiencing specific issues that require them.
• Staking: Ensure the castle nut (which secures the buffer tube to the lower receiver) is properly staked. This prevents it from loosening during use.

Remember, the buffer system works in conjunction with your gas system, BCG, and ammunition to determine how your AR-15 rifle cycles. A standard carbine buffer system from a reputable manufacturer like BCM, Aero Precision, or VLTOR will provide reliable function for most general-purpose builds.

While we won’t go to in too much depth here, also check out VLTOR’s A5 buffer system, and see if it is of interest to you.

The Importance of Staking

Proper staking is a critical step in the AR-15 rifle building process that should never be overlooked. Staking refers to the practice of deforming metal to prevent fasteners from backing out due to recoil and vibration. The two most important areas that require staking are the castle nut (which secures the buffer tube to the lower receiver) and the gas key screws on the bolt carrier group.

For the castle nut, proper staking prevents the buffer tube from rotating and potentially coming loose during use. This is crucial for maintaining the rifle’s reliability and preventing potential damage to the receiver extension and lower receiver. The staking process involves using a punch to deform a small portion of the receiver end plate into one of the notches on the castle nut.

On the bolt carrier group, the gas key screws must be staked to prevent them from backing out. If these screws come loose, it can lead to gas leakage, resulting in reduced reliability and potential malfunctions. Proper staking of the gas key involves deforming a portion of the gas key’s metal over the screw heads.

While some builders may be tempted to skip this step, especially on the castle nut, arguing that proper torquing is sufficient, staking provides an extra layer of security that’s well worth the minimal effort required. It’s a hallmark of a properly built AR-15 and demonstrates attention to detail and commitment to reliability. Remember, many of the most respected AR-15 manufacturers stake these components on their factory rifles for good reason.

If you’re not comfortable performing the staking yourself, consider having it done by a qualified gunsmith. The peace of mind knowing these critical components are secure is well worth the investment.

8. Stock

The stock affects the rifle’s length of pull, cheek weld, and overall ergonomics. For a versatile, general-purpose AR-15 rifle, an adjustable stock is usually the best choice. Here’s what to consider:

• Adjustability: An adjustable stock allows you to change the length of pull to fit different shooters or accommodate varying levels of gear.
• Cheek weld: Look for a stock that provides a comfortable and consistent cheek weld. This aids in maintaining proper eye alignment with your sights or optics.
• Construction: Polymer stocks are lightweight and durable. Some feature reinforced polymer or have aluminum components for added strength.
• Lock-up: The stock should have minimal wobble when extended and lock up securely in each position.
• QD sling mounts: Built-in QD sling attachment points can be very convenient.
• Storage: Some stocks offer small storage compartments for batteries or other small items. While not necessary, this can be a handy feature.

Popular and reliable options include the B5 Systems SOPMOD, Magpul MOE SL, or BCM Gunfighter stocks. These provide a good balance of comfort, durability, and functionality for a general-purpose rifle.

9. Other Essential AR-15 Rifle Components

Several other components are crucial for completing your AR-15 rifle build:

• Charging Handle: This is used to manually cycle the action of your rifle. Standard mil-spec charging handles work fine, but enhanced models offer improved ergonomics and ease of use, especially with optics mounted. Consider ambidextrous models like the Radian Raptor or BCM Gunfighter for enhanced versatility.
• Muzzle Device: For a general-purpose build, a flash hider is often the best choice. It reduces visible flash, which is beneficial in low-light conditions. The A2 flash hider is a simple, effective option. For enhanced performance, consider options like the BCM Mod 0 or Surefire Warcomp, which offer some recoil reduction in addition to flash suppression.
• Gas Block: For a 16″ mid-length barrel, you’ll need a .750″ gas block (this is the most common diameter, but always verify with your barrel specifications). Low-profile gas blocks are preferred for use with free-float handguards. Look for options from reputable manufacturers like BCM, Seekins Precision, or SLR Rifleworks.
• Gas Tube: You’ll need a mid-length gas tube to match your mid-length gas system. Ensure it’s made from durable stainless steel.
• Lower Parts Kit (LPK): This kit contains the small parts needed to complete your lower receiver, including springs, detents, pins, and the magazine release. You can find complete LPKs or partial kits if you’re using an aftermarket trigger or grip.
• Pistol Grip: This is largely a matter of personal preference. Popular options include the Magpul MOE, BCM Gunfighter, or B5 Systems P-Grip. Look for something comfortable that suits your hand size and shooting style.

Remember, even these smaller components play crucial roles in the function and reliability of your rifle. Stick with reputable manufacturers and avoid the temptation to cut costs on these essential parts.

Build an AR-15 Rifle – Must-Have Accessories

At AR15discounts.com, we’ve equipped thousands of AR-15s with essential gear. While the AR-15 platform is highly customizable, there are three accessories that we consider essential for a well-rounded, general-purpose rifle: a weapon light, a red dot optic, and a sling. Let’s briefly discuss the importance of each:

1. Weapon Light

A quality weapon light is crucial for proper target identification, especially in low-light conditions. Remember, you must be able to positively identify your target in any self-defense situation.

• Choose a light with at least 300-500 lumens for adequate illumination.
• Look for durable models from reputable manufacturers like Streamlight, SureFire, or Modlite.
• Consider the mounting position and activation method that works best for your grip and shooting style.

A weapon light isn’t just for home defense; it’s also valuable for general-purpose use, allowing you to navigate and identify targets in any lighting condition.

2. Red Dot Optic

A red dot sight offers quick target acquisition and improved accuracy over traditional iron sights for most shooters.

• Choose a quality, durable optic from proven manufacturers like Aimpoint, Trijicon, or Holosun.
• Look for long battery life and a clear, crisp dot.
• Consider models with multiple brightness settings for versatility in different lighting conditions.
• Ensure the mount is sturdy and maintains zero under recoil.

While iron sights are still valuable as a backup, a red dot optic can significantly enhance your shooting performance and versatility.

3. Sling

A sling is more than just a carrying strap; it’s a crucial tool for weapon retention and shooting support.

• Choose between single-point, two-point, or convertible slings based on your needs and preferences.
• Look for durable materials and quality hardware.
• Ensure the sling allows for quick adjustments for different shooting positions and transitions.
• Popular options include models from Blue Force Gear, Vickers, or Magpul.

A good sling allows you to maintain control of your rifle while using your hands for other tasks, transition to a sidearm if necessary, and can even provide additional stability in certain shooting positions.

Remember, while these accessories are important, they’re not a substitute for proper training and practice. Invest time in learning how to effectively use these tools alongside your AR-15.

Build an AR-15 Rifle – Essential Tools for AR-15 Building

At AR15discounts.com, we often emphasize the importance of having the right tools for your AR-15 build. Proper tools not only make the process easier but also help ensure the safety and reliability of your finished rifle. Here’s a list of essential tools you’ll need:

1. Armorer’s Wrench

This multi-purpose tool is crucial for installing and removing the barrel nut, castle nut, and other components. Look for one with multiple attachments for versatility.

2. Upper and Lower Receiver Vise Blocks

These secure your receivers in a vise without causing damage. They’re essential for stability during assembly and prevent scratches or deformation.

3. Torque Wrench

Critical for ensuring proper torque on components like the barrel nut and castle nut. Correct torque is vital for safety and reliability.

4. Punch Set

Used for installing and removing pins in the lower receiver. Include both standard and roll pin punches in your set.

5. Roll Pin Holder and Starter Punch

These tools make it much easier to start and drive in roll pins without bending or damaging them.

6. Bench Vise

A sturdy bench vise provides a stable platform for your work. Ensure it has enough clamping force for various components.

7. Gunsmithing Screwdriver Set

A set of precision screwdrivers is necessary for adjusting and assembling small components without damaging them.

Additional Useful Tools

• Headspace gauges for checking proper chamber dimensions
• Cleaning supplies for maintenance during and after assembly
• Safety glasses and gloves for personal protection

A Note on Tool Quality

While it might be tempting to cut costs on tools, we at AR15discounts.com always recommend investing in quality tools. They’ll last longer, perform better, and reduce the risk of damaging your rifle components during assembly.

Caution: Proper Use of Tools

Remember, having the right tools is only part of the equation. Proper use of these tools is crucial. If you’re unsure about how to use a particular tool or perform a specific step in the assembly process, don’t hesitate to seek guidance from experienced builders or professional gunsmiths.

AR-15 Specific Tool Kits

For those looking for a comprehensive solution, we offer AR-15 specific tool kits that contain most, if not all, of the tools you’ll need for your build. These kits can be a convenient and cost-effective way to ensure you have the right tools for the job.

By ensuring you have these essential tools on hand before starting your build, you’ll be well-prepared to assemble your AR-15 safely and effectively. Remember, a well-built AR-15 starts with the right tools and knowledge.

Build an AR-15 Rifle – Conclusion

To build an AR-15 rifle is an exciting journey. By focusing on quality components, particularly for critical parts like the barrel, bolt carrier group, and trigger, you can create a versatile rifle suitable for a wide range of applications.

Remember, the goal in building an AR is ensuring reliability and functionality. A 16″ barrel with a mid-length gas system provides an excellent foundation for a do-it-all rifle. Paired with a quality bolt carrier group, a decent trigger, and other carefully selected components, you’ll have an AR-15 that’s capable of everything from home defense to recreational shooting and even competition.

Take your time with the building process, follow proper assembly procedures, and don’t neglect crucial steps like proper staking. Once your rifle is complete, equip it with essential accessories like a weapon light, red dot optic, and sling to maximize its versatility and effectiveness.

At AR15discounts.com, we’re committed to helping you make informed decisions about your AR-15, whether you’re building from scratch or looking for quality components. Remember to always prioritize safety, invest in quality ammunition, and seek proper training to become proficient with your new rifle.

Stay safe, train hard, and enjoy your new firearm responsibly. And remember, whether you need individual components or expert advice, we’re here to help you every step of the way.