# Build Your Own High-Performance AR-9 Carbine: A Comprehensive Guide to the RK9-FSSK15-NL Kit

Are you considering building a Pistol Caliber Carbine (PCC) but feeling overwhelmed by the sheer number of components and compatibility issues? Or perhaps you're an experienced enthusiast looking for a high-quality, reliable foundation for your next 9mm AR project? Look no further. The RK9-FSSK15-NL Complete AR-9 Unassembled Kit offers a streamlined, comprehensive solution for constructing a basic functioning 9mm AR, delivering both performance and the satisfaction of a do-it-yourself firearm build.

This kit, meticulously curated and available from trusted sources like DEGuns.com, is designed to simplify the process of assembling a robust and enjoyable AR-9. It’s ideal for new builders keen to learn the mechanics of the AR platform with a forgiving 9mm cartridge, or for seasoned builders who appreciate the convenience of a nearly-complete package featuring premium components. Whether your goal is a versatile home defense carbine, a cost-effective training platform, or a fun addition for range days and competitive shooting, this kit provides the essential elements to get you started.

Why Choose to Build an AR-9?

Building an AR-9 offers several compelling advantages over purchasing a factory-assembled unit:

• Cost-Effectiveness: Often, assembling a quality AR-9 from components can be more economical than buying a complete rifle, allowing you to allocate savings to optics, ammunition, or additional accessories.
• Customization from the Ground Up: You gain intimate knowledge of your firearm's mechanics, empowering you to tailor every aspect to your specific preferences, from trigger feel to stock ergonomics.
• Educational Experience: For new builders, the assembly process provides invaluable insights into the AR platform, fostering a deeper understanding of its operation, maintenance, and potential for future modifications.
• Ammunition Versatility: The 9mm cartridge is widely available, relatively inexpensive, and suitable for a variety of shooting scenarios, including plinking, target practice, and even self-defense applications within appropriate contexts. Its lower recoil makes for a more comfortable shooting experience, especially during extended range sessions.
• Reduced Recoil and Noise: Compared to traditional rifle calibers, 9mm offers significantly less recoil and muzzle blast, making it a favorite for indoor ranges or for shooters seeking a gentler experience.

This kit answers the critical question: "What are the essential parts I need to build a reliable AR-9 carbine, excluding the lower receiver?" It provides nearly every major component, ensuring compatibility and quality without the guesswork of sourcing individual parts from various manufacturers.

Key Components and Their Performance Benefits

The RK9-FSSK15-NL kit is thoughtfully assembled with components chosen for their durability, performance, and compatibility. Each part plays a crucial role in the overall functionality and feel of your finished AR-9.

• Chambered: 9mm
  The decision to chamber this kit in 9mm is foundational to its appeal. This ubiquitous pistol cartridge offers an excellent balance of affordability, manageable recoil, and terminal performance for carbine applications. It's a fantastic choice for training, competition, and general range use due to its widespread availability and lower cost compared to rifle ammunition. When considering a "best pistol caliber carbine" for versatility, 9mm consistently ranks high.
• Bolt Carrier: Colt/Glock Compatible Black Nitride 9mm
  The heart of any blowback AR-9 system is its bolt carrier group (BCG). This kit features a 9mm bolt carrier specifically designed for compatibility with both Colt-style and Glock-pattern magazines, offering maximum flexibility when choosing your lower receiver or magazine preference. The Black Nitride finish isn't just for aesthetics; it provides exceptional hardness, corrosion resistance, and reduced friction, leading to smoother cycling, easier cleaning, and enhanced longevity. This is a critical component for reliable feeding and extraction, ensuring your AR-9 operates flawlessly.
• Barrel: 16" 1:10 Twist 4150 Chrome Moly Steel Barrel Black Nitride Threaded 1/2x36
  The barrel is the cornerstone of accuracy. This 16-inch barrel ensures your build qualifies as a rifle, avoiding complex NFA regulations often associated with shorter barrels.
  • 1:10 Twist Rate: This twist rate is optimally suited for stabilizing the common 9mm bullet weights, promoting excellent accuracy and consistent performance with a wide variety of ammunition. If you're wondering "what twist rate is best for 9mm AR?", 1:10 is a widely accepted standard.
  • 4150 Chrome Moly Steel: This high-strength steel alloy is renowned for its durability and resistance to wear, making it an excellent choice for a barrel that will see significant use.
  • Black Nitride Finish: Similar to the bolt, the nitride treatment on the barrel enhances surface hardness, corrosion resistance, and improves lubricity, contributing to a longer barrel life and easier cleaning.
  • Threaded 1/2x36: This specific threading is crucial for attaching muzzle devices. Note that 1/2x36 is the standard for 9mm AR barrels and differs from the 1/2x28 common on 5.56/.223 barrels. This ensures proper fitment for 9mm-specific muzzle brakes or suppressors.
• Rail: 15" Super Slim Keymod w/ Steel Barrel Nut
  A 15-inch handguard provides ample rail space for mounting accessories like lights, lasers, foregrips, and slings, while fully enclosing the 16-inch barrel for a sleek, integrated look.
  • Super Slim Design: This ergonomic profile offers a comfortable and secure grip, enhancing control and maneuverability.
  • Keymod Attachment System: Keymod slots along the handguard provide a lightweight and efficient method for attaching various accessories. While newer systems exist, Keymod remains a popular and functional choice for many builders.
  • Steel Barrel Nut: The use of a robust steel barrel nut ensures a secure and stable connection between the handguard and the upper receiver, minimizing flex and maintaining zero for mounted optics or aiming devices.
• Upper: Mil-Spec AR-15 Upper W/ Forward Assist, Charging Handle & Dust Cover Assembly
  This kit includes a complete, ready-to-assemble Mil-Spec AR-15 upper receiver.
  • Mil-Spec Standard: Adhering to military specifications ensures dimensional consistency and compatibility with a wide range of aftermarket parts, simplifying future upgrades or customization.
  • Forward Assist: While less critical on a blowback 9mm AR than on a direct impingement rifle, the forward assist is included for a standard AR-15 aesthetic and, in rare instances, to ensure the bolt is fully seated.
  • Charging Handle: A standard AR-15 charging handle provides reliable operation for cycling the bolt and clearing the chamber.
  • Dust Cover Assembly: Protects the internal components from dust, dirt, and debris, especially important for maintaining reliability in various environments.
• Stock: M4 Style Stock w/ Adjustable 6 Position Buffer Tube Assembly w/ Heavyweight Custom 9mm Buffer
  The M4 style stock is a highly popular and versatile choice, offering comfort and adjustability.
  • Adjustable 6-Position Buffer Tube: This allows you to fine-tune the length of pull to fit various shooters and shooting positions, enhancing comfort and control.
  • Heavyweight Custom 9mm Buffer: This is one of the most critical components for reliable AR-9 operation. Due to the blowback nature of 9mm ARs, a heavy buffer is essential for proper cycling, mitigating bolt bounce, and reducing felt recoil. The custom heavyweight buffer included in this kit is specifically designed to manage the unique recoil impulse of the 9mm cartridge, leading to a smoother, more enjoyable shooting experience and extended component life. If you're asking "what buffer do I need for an AR-9?", a dedicated heavyweight 9mm buffer like this one is the correct answer.
• Muzzle: Multi Ported Competition Style Brake
  This kit includes a multi-ported competition-style muzzle brake, engineered to significantly reduce recoil and mitigate muzzle rise. This allows for faster follow-up shots and improved accuracy, particularly beneficial in dynamic shooting scenarios or competitive events. The design channels expanding gases to counteract muzzle movement, making for a flatter shooting experience.
• AR-15 Lower Parts Kit (LPK) Included
  To truly offer a comprehensive package (excluding the lower receiver itself), this kit comes with a standard AR-15 Lower Parts Kit. This LPK contains all the necessary small components to complete your chosen lower receiver, including the trigger group, safety selector, magazine release, bolt catch, pivot and takedown pins, and all associated springs and detents. This means you won't need to source these crucial small parts separately, streamlining your build even further.

The Crucial Missing Piece: Your Lower Receiver

It’s important to note that the lower receiver is not included in this kit. This is intentional and offers the builder maximum flexibility:

• Legal Compliance: The lower receiver is the serialized "firearm" component by law, requiring transfer through an FFL (Federal Firearm Licensee). By not including it, this kit can be shipped directly to your door, allowing you to acquire the lower receiver separately from your preferred FFL or, in some cases, to build an 80% lower yourself (subject to local and federal regulations).
• Personal Choice: Builders can select a lower receiver based on their aesthetic preferences, desired magazine compatibility (e.g., dedicated Glock-mag lowers, Colt-mag lowers, or standard AR-15 lowers with magwell adapters), or material (forged, billet, polymer). For optimal performance with the included Colt/Glock compatible bolt, a dedicated 9mm lower or a high-quality magwell adapter for a standard AR-15 lower is highly recommended. Many builders prefer dedicated 9mm lowers for their robust feeding characteristics.

Assembling Your AR-9: What to Expect

Building an AR-9 from this kit is a rewarding project for anyone with basic mechanical aptitude. While specific instructions are typically provided with the components, the general process involves:

1. Lower Receiver Assembly: Installing the Lower Parts Kit (LPK) into your chosen 9mm-compatible lower receiver.
2. Upper Receiver Assembly: Attaching the barrel to the upper, installing the handguard, and then adding the charging handle, bolt carrier group, and dust cover.
3. Buffer System Installation: Placing the heavyweight 9mm buffer and spring into the buffer tube, which then attaches to the lower receiver along with the adjustable stock.
4. Final Assembly: Mating the completed upper and lower receivers.

Tools commonly needed include an armorers wrench, punches, a hammer, a vice block for the upper and lower, and eye protection. Many resources, including detailed guides and video tutorials, are available to walk first-time builders through each step, ensuring a successful and safe assembly.

Why Choose DEGuns.com for Your Kit?

When investing in firearm components, trust and reliability are paramount. DEGuns.com is a reputable source for quality firearm parts and accessories. The availability of the RK9-FSSK15-NL kit through DEGuns.com ensures you are receiving a genuine product with the specified components, backed by a commitment to customer satisfaction. This comprehensive kit provides the ultimate foundation for your AR-9 build, simplifying the parts acquisition process and allowing you to focus on the enjoyable assembly.

Frequently Asked Questions (FAQ) About Building an AR-9

• Is an AR-9 good for home defense?
  Yes, an AR-9, particularly with its 16-inch barrel and effective muzzle device, can be an excellent choice for home defense. The 9mm cartridge offers reduced over-penetration concerns compared to traditional rifle rounds in an indoor environment, while still providing sufficient stopping power. Its lighter recoil and adjustable stock make it manageable for various users, and the ability to mount lights and optics enhances its utility.
• Can I use my existing AR-15 lower?
  Yes, you can use a standard AR-15 lower receiver, but you will need a dedicated 9mm magazine well adapter (often called a "mag block") to use 9mm magazines, such as Glock or Colt SMG magazines. For optimal reliability and simplicity, many builders prefer dedicated 9mm lower receivers that natively accept Glock or Colt magazines without an adapter, as they are designed specifically for the 9mm blowback system. The bolt in this kit is compatible with both Colt and Glock magazine patterns, offering flexibility regardless of your lower choice.
• What kind of accuracy can I expect from an AR-9?
  With a quality barrel like the 16" 4150 Chrome Moly barrel included in this kit, paired with the correct 1:10 twist rate, you can expect excellent accuracy at typical pistol caliber carbine ranges (25-100 yards). Many AR-9s are capable of 1-3 MOA (Minute of Angle) groups, especially with good quality ammunition.
• Why choose a heavyweight 9mm buffer?
  AR-9s operate on a simple blowback system, meaning there's no gas tube or rotating bolt like a standard AR-15. The heavier bolt and buffer absorb the recoil impulse and ensure the bolt cycles correctly, preventing "bolt bounce" (where the bolt briefly bounces off the breech face upon closing, potentially leading to misfires or malfunctions). A heavyweight buffer is crucial for reliable and smooth operation, reducing felt recoil and extending the life of your components.
• What's the difference between 1/2x36 and 1/2x28 threading?
  These numbers refer to the thread pitch on the barrel muzzle. 1/2x28 is the common standard for 5.56/.223 AR-15 barrels, while 1/2x36 is the standard for 9mm AR barrels. It's critical to use a muzzle device or suppressor designed for the correct thread pitch to ensure proper fitment and safe operation. This kit features the correct 1/2x36 threading for 9mm.

Your Journey to Building a Custom AR-9 Starts Here

The RK9-FSSK15-NL Complete AR-9 Unassembled Kit provides a robust and reliable foundation for your next firearm project. By providing high-quality, compatible components, it removes much of the guesswork from the building process, allowing you to focus on the rewarding experience of assembling your own pistol caliber carbine. Whether you're a first-time builder or a seasoned enthusiast, this kit, available through trusted retailers like DEGuns.com, is an excellent investment in your shooting pursuits.

---

Product Specifications & Component Breakdown

Feature	Detail	Benefit
Caliber	9mm	Affordable, low recoil, widely available ammunition.
Barrel	16" 1:10 Twist 4150 Chrome Moly Steel, Black Nitride, Threaded 1/2x36	Optimal accuracy, durability, corrosion resistance, muzzle device compatibility.
Bolt Carrier	Colt/Glock Compatible Black Nitride 9mm	Versatile magazine compatibility, smooth operation, enhanced durability, easy cleaning.
Handguard	15" Super Slim Keymod w/ Steel Barrel Nut	Ample accessory space, ergonomic grip, secure attachment.
Upper Receiver	Mil-Spec AR-15 W/ Forward Assist, Charging Handle & Dust Cover	Standardized fit, complete assembly, protection from elements.
Stock System	M4 Style Stock w/ Adjustable 6 Position Buffer Tube & Heavyweight Custom 9mm Buffer	Custom fit, recoil management, reliable cycling for blowback system.
Muzzle Device	Multi Ported Competition Style Brake	Reduced recoil, mitigated muzzle rise for faster follow-up shots.
Lower Parts Kit	AR-15 Lower Parts Kit (LPK) Included	All small components needed to complete your lower receiver.
Lower Receiver	NOT INCLUDED	Allows for personal choice, legal compliance, or 80% lower build.
SKU / Identifier	RK9-FSSK15-NL	Unique product identifier for this specific kit.