Build AR 9

How to Build AR 9?

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Build AR 9

AR 9s are usually chambered to shoot the 9mm Luger rounds. They are designed with shorter barrels and are lightweight compared to their counterparts AR 15. What makes the AR 9 unique? Unlike a AR 15 that uses the piston system or direct impingement, it uses the blowback action. Also, the barrel, Bolt Carrier Group, magazine, and Lower Receiver are 9mm.

The AR 9 is a reliable firearm among other AR platform guns. Additionally, it has minimal recoil and allows easier maneuverability.  However, due to the short length barrel, their accuracy is precise at short ranges.

What parts do you need to build a AR 9, and what is the process of building one? Our article outlines the necessary parts you ought to buy before you embark on building a AR 9 gun. We have also provided you with an easy step-by-step guide on how to build the same firearm. It will give you an overview of what you need to do to build a functional AR 9.

How to Build AR-9
Build AR 9

Parts Needed to Build a AR 9

  • 9mm Lower Receiver (installed with a Magazine Release and Ejector)
  • 9mm Bolt Carrier Group
  • An AR Upper Receiver
  • 9mm Buffer Tube Kit
  • 9mm Bolt
  • 9mm Magazine
  • AR Charging Handle
  • 9mm Barrel (no hole for gas block)
  • Muzzle device
  • Bolt Catch
  • Trigger Group Assembly
  • Brace
  • Extractor
  • Sights
  • AR 9 Lower Parts Kit
  • Trigger Assembly
  • Grips
  • MLOK Handguard

Significant Tools for Assembling a AR 9

  • Torque Wrench
  • Roll Pin Punch Set
  • Armors Wrench
  • Detent Pin Holder
  • Vise Block

Step by Step Build Guide of a AR 9

AR 9 Upper Receiver Assembly

  • The first step while building your AR 9 will entail assembling your AR 9 Upper Receiver.
  • Start by installing your Charging Handle and Bolt Carrier Group into the Upper.
  • On the rear end of the Upper Receiver, there is a slot for both of the above.
  • First, slide in the Charging Handle halfway, then slide in the Bolt Carrier Group into its respective slot. Then push in both parts all at once till they lock-in.
  • Ensure the move in and out freely.
  • Fix in your Barrel into the front end of the Receiver.
  • Apply some grease on the rear end of the Barrel that will be going into the Receiver.
  • Ensure that the Barrel is well-positioned and aligns with the little notchon the threaded area before inserting your barrel nut.
  • Also, tighten the Barrel Nut to the right torque. It’s time to utilize your Vise Block, Torque Wrench, and Armors Wrench
  • Insert your Muzzle Device on the front end of your Barrel. Also, ensure you use a Crush Washer before you thread in the Muzzle Device.
  • Now, position your MLOK Handguard over the Barrel and screw it up.
  • You have a complete Upper Receiver, and it’s time you assemble the Lower Receiver.

AR 9 Lower Receiver Assembly

  • Start by installing your Extractor on its slot. Also, ensure you tighten it using screws.
  • Insert the Detent Spring and the Detent into the Receiver. It should be accompanied by the Takedown Pin that holds its place.
  • Push in the Takedown Pin until it clicks into place with the Detent.
  • Fix in your Safety Selector into the Lower Receiver.
  • Time to work on your grip.On the bottom side, there is a hole for the Detent Spring. Drive it in.
  • Insert a Detent on the Lower Receiver in its slot where it joins to the Pistol grip.
  • Now join your Pistol Grip to the Receiver. Also, insert a screw on the grip’s bottom side to hold it tight to the Receiver.
  • Ensure your Safety Selector works as required.
  • Install your Bolt Catch and Bolt Catch Spring.
  • Fix in the Bolt Catch on its hole.
  • Then take the Bolt Catch Spring and Bolt Catch Plunger and drop them into the respective located on the Lower Receiver’s side.
  • Assemble your Trigger Group Assembly. Also, ensure everything is correctly aligned, more so the Trigger Spring.
  • Adjust your Safety Selector to “safe.”
  • Now, drop in your Trigger Assembly Group into the Lower Receiver. Ensure you position it underneath the Safety Selector. Additionally, align it appropriately before you insert a Detent to hold it in place.
  • Insert your Hammer Assembly into the Receiver.
  • Ensure the trigger functions correctly.
  • It’s time to install your Buffer Tube Assembly.
  • Start by pushing in a Detent followed by a Spring to the rear end on your Receiver. A Detent Holder will assist you in fixing the two.
  • Apply some grease on the threaded front end of the Buffer Tube.
  • Install the Buffer Tube accompanied by a Castle Nut that pushes in the Spring you inserted on the Receiver.
  • Also, do not forget to tighten up the entire set up before adding your Stabilizing Brace into the Buffer Tube.
  • Now, push in your Buffer Spring and Buffer into the Buffer Tube.
  • Use your thumb to push it in and out to ensure there it has enough tension.
  • You may add Red Optic Sights on our Handguard.
  • Now you have a complete Lower Receiver Assembly.
  • It’s time you combine the Upper and Lower Receiver Assemblies.
  • Cock back the hammer
  • Align the Pivot Pinholes on the Lower and Upper Receiver and then Push in the Pivot Pin
  • Push down your Upper and lock it in position using another pin on the right side of your Lower Receiver.
  • Conduct a test function of your AR 9 and see how everything works.
  • Feed your 9mm Magazine with quality rounds and load your firearm.
  • Get a safe place to shoot as you assess the experience with your built AR 9.


Building a AR 9 is a good experience and similar to that of building a AR 15. However, they differ in some of their parts. For instance, an AR 9 does not have a Gas Key, Gas Tube, and Gas Block because it uses a blowback system to operate.

The above guide will help you assemble all the parts of a standard AR 9 in pistol or rifle form as long as you have the right parts and tools for the task. Also, ensure you observe gun safety rules to avoid injuries while building your AR 9. For more information about Gun sales in the USA, visit our hub.