Designing Your AR
Your rifle is only as good as the decisions behind it. This is our curated library of AR-15 design resources — from buffer systems to barrel accessories. Whether you’re building your first rifle or refining your fiftieth, start here to learn what matters and why.
📐 Defining the Build
TIf you’re building or modifying an AR-platform firearm, you may be just one misstep away from federal prison. The National Firearms Act has been entangling the uninformed and irresponsible since 1934.
This article explores the major elements of NFA, how they affect your build, and how you can stay on the right side of the law.
The class of AR pretty much defines what you can do with the gun.
This article explores the selection of AR class. We look at the pistol caliber (i.e. “pistol caliber carbine”), small frame (a.k.a. AR-15), and large frame (a.k.a. AR-10 or LR308) AR.
You’ve seen it stamped on boxes, featured in ads, and dropped in conversations like gospel: Mil-Spec. But what does it really mean?
Two of the best things about the AR platform are standardization and modularity. So many of the components can be used across all classes and manufacturers. But not all.
Here, we offer tables of compatibility of components across AR classes. No more guessing, buying, trying, buying, trying.
🧱 Platform Components
The lower receiver is the serialized heart of the AR — it houses the fire-control group, anchors the buffer system, and defines how the upper, stock, and controls interface.
This guide explains receiver types, key design features, finishes, and buyer guidance to help you choose the right lower for your build.
The upper receiver is more than just the top half of the rifle — it’s the foundation of precision and reliability. It houses the bolt carrier group, aligns the barrel, and defines the optic rail that ties the entire system together.
In this article, we break down the design elements that determine performance and consistency, including materials, finishes, machining tolerances, and top profile.
The handguard affects barrel clearance, accessory mounting, ergonomics, and heat management — all of which impact safety and reliability.
In this article, we explain drop-in vs. free-float mounting, M-LOK vs. quad rail systems, suppressor and gas block clearance, and how to select the right length and profile for your build.
The platform is the heart of the AR. Choosing the right platform from the start can make or break your firearm’s potential. The right platform can take you from a entry level gun through a competition level gun, with unlimited upgradeability.
This article explores the selection of AR platform and evaluates the common options in the market.
⚙️ Core Operating System Components
The muzzle device is more than just a pretty face; it can directly contribute to the performance of a weapon.
In this article, we explore the design elements and types of muzzle devices, including flash hiders, compensators, muzzle brakes, blast forwarding devices, sound suppressors, and hybrid devices.
Whether you are buying a factory barrel or designing a custom barrel, barrel selection is one of the most important decisions in the design process.
This article provides a summary of selection criteria. For more, check out our Barrel Deep Dive series!
The gas block has one of the most important jobs in the AR. Selecting the right gas block can make or break your build.
In this article we review the different gas block designs, as well as the benefits and limitations of each.
The bolt carrier group is the heart of the AR. It is part gas system, part cartridge manager, and part reciprocating mass. It is a beautiful feat of engineering, the way it was designed. Yet, the AR enthusiast is faced with dozens of design options.
In this article, we cover the basics of BCG design and selection, and walk you through the truth and the gimmicks.
The buffer and spring system plays a critical role in controlling bolt speed, recoil impulse, and cycling reliability. This guide explains how to select and tune buffers for suppressed rifles, SBRs, precision setups, and more. Covers carbine, A5, and rifle buffers, weight configurations, spring compatibility, and troubleshooting gas-related symptoms.
The operating system of the AR is a complex and interdependent collection of components.
In this article, we explore the buffer spring and how it contributes to the proper function of the AR platform. We discuss the four types of buffer springs, their benefits, and our recommendations.
The buffer tube (receiver extension) anchors your entire recoil system and defines how your stock or brace interfaces with the rifle. It’s easy to forget this important component when you hide it under a stock — but it can have a profound impact on reliability, recoil, and parts compatibility.
In this article, we explore the AR buffer tube.
The trigger is one of the most important components of any firearm and there are a lot of flavors of trigger.
This article explores the construction and operation of the trigger system. We review the design parameters, the options, and how pick the best combination for your use case. We offer our recommendations on both brands and triggers, with a comparison for each of our favorites.
It may seem strange to dedicate an article to pins; but there is a lot of pervasive misinformation out there.
In this article, we explore the three categories of hammer and trigger pins, why you might consider each of them, and when (if ever) to avoid each of them.
🕹️ Controls
The charging handle is your manual link to the bolt carrier group — and your first line of control under stress.
This article explores how charging handle design affects ergonomics, reliability, suppressed performance, and build-specific compatibility.
The safety selector controls the most important interface between shooter and fire control group — safe or fire. Whether you’re building for speed, precision, or ambidextrous use, this small part has major ergonomic consequences.
In this article, we break down selector throw angles, ambi vs. single-side controls, material, fitment, legal considerations, and how to choose the right selector for your AR build.
Whether you’re building a competition carbine, a duty rifle, or a featureless state-compliant AR, the magazine catch and release button play a bigger role than most shooters realize.
In this guide, we’ll break down how they work, what matters in its design, and how to choose the right one for your build.
The bolt catch may be small, but it’s critical for reload timing, malfunction clearance, and how your rifle runs under pressure.
This guide walks through how the bolt catch works, what influences its design, and how to select the right one for your platform, use case, and controls setup.
They might be small, but pivot and takedown pins directly affect how you field strip, clear malfunctions, and configure your AR for duty or compliance.
In this guide, we’ll cover how they work, which design features matter, and how to choose the right pin set for your build.
🪑 Furniture and Ergonomics
The buttstock of the AR is one of the most important interfaces between you and your gun. It affects everything from length of pull to sight alignment.
This article dives into everything you need to know before selecting a buttstock that will fit your body, your use case, and your shooting style.
The pistol grip is one of the primary interfaces between the shooter and the weapon system. Selection of a pistol grip can have dramatic effects on control, comfort, and consistency.
This article evaluates the design options and helps you pick the best grip for you.
Foregrips and stops can enhance your ability to control your weapon. However, each option comes with its benefits and drawbacks.
This article explores the options and applications of vertical foregrips, angled foregrips, hand stops, finger stops, and barricade stops.
🧠 Special Topics
The AR market is flooded with an alphabet soup of metals and finishes.
In this article, we explore the different types of metals, their properties, their applications, and what to watch out for. We also cover a wide array of finishes and coatings, including performance measures and applications. As always, we try to present as much as possible in as objective a way as possible.
The length of your handguard is more than just a cosmetic choice; your safety depends on it.
In this article, we explore the considerations for choosing a handguard length and the consequences of choosing unwisely. We offer a formulaic approach to find that Goldilocks length, based on your gas system length, barrel length, and muzzle device.
Roll pins can be found throughout the AR-15. When they fail, bad things happen. Yet, they are almost certainly the least considered component in the weapon system.
In this article, we explore the subtle differences between retention pins, including solid pins, slotted pins, and coiled pins.
You can build the AR in dozens of calibers and cartridges.
This article explores the most popular cartridge options for each platform (AR-9, AR-15, and AR-10). For each option, we identify the components that are cartridge-specific, as well as our top picks for those components.
The two primary cartridges in the AR platform have siblings, and they don’t always play nice.
This article explores the two primary calibers of the AR platform, as well as the compatibility of the sister cartridges for each.
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