AR-15 9mm Conversion kit

Best AR-15 9mm Conversion Kits

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You might be reading this because you already have an AR-15 or planning to get your very first AR-15. And now you want to use it more. A great way to get more use and have more fun with your AR-15 is to convert it to a 9mm. I’ll let you know how to do this and what you need to do it. But first, let’s quickly summarise the best 9mm Conversion Kits for your AR-15.

Best AR-15 9mm Conversion Kits

Best Budget Pick
Stern Defense MAG-AD9 AR-15 9mm Conversion Adapter
  • Works with both Glock-style 9mm and .40-caliber magazines
  • Built out of durable 4140 steel alloy
  • Has a built-in magazine release
  • Does not work for pistol magazines other than Glock
  • Requires the use of a Glock cut bolt
$179 Shop NowClick to read my review
Top Pick
Hahn Precision AR-15 Bottom 9mm Adapter
  • Available in top-loading or drop-loading versions
  • Compatible with Colt and Uzi magazines
  • Has a built-in hold open feature on the last round fired
  • Not compatible with Glock magazines
$266 Shop NowClick to read my review
Rock River Arms AR-15 9mm Magwell Conversion Block
  • Built out of durable steel and aircraft-grade aluminum
  • Designed to function with Colt and Uzi magazines
  • Allows you to use the standard magazine catch on your AR-15
  • Not compatible with Glock magazines
  • Does not lock open on Uzi magazines but will with Colt magazines
$245 Shop NowClick to read my review

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Why Convert your AR-15 to a 9mm?

  • If you have a 9mm Luger, it keeps things simple by having two firearms that fire the same caliber.
  • Some AR-15s in 9mm will accept Glock factory magazines, so you can swap magazines with your 9mm Glock.
  • Pistol magazines are lighter and smaller than rifle magazines.
  • Smaller than the 5.56 round, the 9mm has reduced recoil and makes faster follow-up shots easier.
  • The 9mm creates less noise and muzzle flash than the 5.56. This reduces disorientation when you shoot. For home defense, your AR-15 will be more effective in the tight confines of your home.
  • A good home defense setup can include a pistol and carbine with the same magazines and ammunition as a 9mm.

If you think one of these reasons will benefit you, you have two options. You can either buy an AR-15 in 9mm, such as an AR-9, or convert your AR-15 into a 9mm version. In this article, I will talk about how to perform the conversion using a 9mm conversion kit. I will be comparing these three kits so we can see which one would be the best choice for you.

Are you familiar with the conversion process for the AR-15? If yes, then skip our guide and head straight to our comparison section.

A Brief Look at How the Conversion Process Works

Best 9mm Conversion Kits Great Lakes AR-15
Image source: Sportsmans Guide

One of the biggest benefits of the AR-15 is the fact that it is among the most modular firearms in existence. Even if your AR-15 wears a design made to fire centerfire rifle ammunition, such as 5.56x45mm NATO, you can still convert it to fire pistol ammo like the 9mm. You will need to make a handful of modifications. Investing in a new conversion kit is one of those modifications.

How To Convert an AR-15 Into a 9mm Luger

Best 9mm Conversion Kits Lead Star Arms Prime 16" Carbon Fiber Wrapped PCC 9mm AR-9 Rifle
Image source: Palmetto State Armory

I’ve mentioned earlier that the AR-15 is the most modular rifle in existence. What this means is that it is the “LEGO of the firearms world.” In short, it is extremely simple to make adjustments and modifications to this weapon.

To convert your AR-15 into a 9mm Luger would, in essence, be transforming it into an AR-9.

You need to replace your bolt carrier group (BCG) with a new 9mm BCG. You will also need a complete conversion upper receiver to fit into the lower receiver. This will enable you to use your existing 5.56 lower receiver with a 9mm upper receiver. Alternatively, you could get a 9mm AR lower

Another way of doing it would be to keep the existing upper receiver. You should replace the barrel, bolt, and magazine adapter with those that can fit 9mm-sized magazines like Colt, Uzi, or Glock.

Building an upper receiver into the 9mm Luger is cheaper than you might imagine. You need to replace the BCG and the buffer with 9mm models. Afterward, insert a block into the magazine well ― prepare a barrel nut wrench for this. We have a buyer guide on the best 9mm AR buffers ready for you.

I recommend a conversion kit because it is more affordable than separate pieces. Buying separate pieces will add up in price fairly quickly. It might even overtake the price of purchasing a brand new AR9 carbine or pistol.

A Do-it-Yourself Project

Installing a 9mm barrel into your upper receiver isn’t hard, and it doesn’t require the aid of a gunsmith. The back of a 9mm barrel has the same size and diameter as a 5.56 barrel, and the barrel nuts are the same as well. So, all you need to do is torque the barrel nut in with your handguard of choice.

A chief difference between a 9mm barrel and a 5.56 barrel is that the muzzle threads are different. This forces you to invest in a flash hider, compensator, or any other muzzle device designed specifically for the 9mm. Shooters do this to avoid the chance of a catastrophic failure. Then, you need to replace the 5.56 bolt with a 9mm bolt. You may keep the buffer and charging handle of your 5.56 version.

At this point, the only thing left is to purchase a special adapter for 9mm magazines. Choose one that can feed 9mm ammunition into the chamber reliably. It is these special adapters that we will be discussing later in this guide.

These adapters come in two primary forms

  1. One you can insert beneath the lower receiver and held in place with the magazine catch, and
  2. One tyou can insert through the top of the lower receiver and held by the lips of the receiver. For our purposes, there is no significant difference between the two.

You can complete the entire conversion in a matter of minutes. Furthermore, switching back to 5.56 AR is very easy. It is the exact reverse of the process above. Get rid of the magazine adapter and replace the barrel, buffer, and BCGs with the 5.56 models.

Here’s a quick video from Brownells showing us how to convert your AR rifle:

Factors To Consider When Choosing a Conversion Kit

  • Magazine Compatibility: The most common magazine types for the 9mm AR-15 are the Glock, Colt-style, and Uzi magazines. Most conversion kits can handle both Colt and Uzi magazines but not Glock. You have to consider what pistol you have or will buy to maximize magazine compatibility.
  • Durability: The best kits are made from high-quality steel and/or aircraft aluminum. They are often coated further in a rust- and corrosion- resistant finish, such as nitride. As your kit will be part of your gun, it needs to be built to the same standards as your actual AR.
  • Ease of Installation: For the process to be as stress-free as possible, your conversion kit should have a drop-in design. That means that the kit can be installed into the AR-15 without any specialized tools.
  • Last Round Hold Open Feature: Will the conversion kit ensure that the AR-15 bolt will hold open on the last round fired? It might not impact weapon reliability, but it is a nice feature to have.
  • Reliability: Your kit should allow reliable feeding of ammunition from the magazine into the AR-15. If the follower angle of the kit is too steep, it can cause feeding issues to occur. This is particularly common with the last four to five rounds in the magazine.

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Conversion Kit Comparison

Conversion KitMaterialMagazine StyleLast round hold open feature?
Stern Defense MAG-AD9 AR-15 9mm Conversion Adapter4140 alloy steelGlock-style 9mm double-stack magazinesYes
Hahn Precision AR-15 Bottom 9mm Adapter6061 billet aluminum Colt and Uzi magazinesYes
Rock River Arms AR-15 9mm Magwell Conversion BlockSteel and aircraft-grade aluminumColt and Uzi magazinesNo

Stern Defense MAG-ADR AR-15 9mm Conversion Adapter

Best 9mm Conversion Kits Stern Defense MAG-ADR AR-15 9mm Conversion Adapter
Image source: cdn-bjeckh.nitrocdn.com

The Stern Defense MAG-ADR AR-15 9mm Conversion Adapter is an excellent choice for an AR-15 9mm adapter. Originally, it was made out of high-quality aircraft grade 6061 aluminum. The manufacturer changed it later to the even more durable 4140 alloy steel.

This conversion adapter has a design where you can use it with Glock-style 9mm double-stack magazines. It can work with Glock factory magazines. For aftermarket ones, you would have to check compatibility individually. It can also fit .40 caliber double-stack Glock magazines, in case you want to convert your AR-15 to a .40 S&W caliber instead.

Best 9mm Conversion Kits Stern Defense MAG-ADR AR-15 9mm Conversion Adapter
Image source: cdn-bjeckh.nitrocdn.com

This conversion adapter also comes with a last-round hold-open feature. This means that the bolt to your AR-15 will lock back when you fire the last round out of the magazine. It also has a built-in magazine release so that it’s easy to eject spent magazines.

Take note that this conversion adapter also requires the use of a Glock cut bolt. You may need to shave a little off the top of the ejector to install it, depending on the bolt you are using.

Pros
  • Works with both Glock-style 9mm and .40-caliber magazines
  • Built out of durable 4140 steel alloy
  • Has a built-in magazine release
  • Has a last round bolt hold open feature
Cons
  • Does not work for pistol magazines other than Glock
  • Requires the use of a Glock cut bolt
Best 9mm Conversion Kits Stern Defense MAG-ADR AR-15 9mm Conversion Adapter
Image source: cdn-bjeckh.nitrocdn.com

The Stern Defense adapter is a solid choice if you will use Glock magazines. It’s built out of very durable 4140 steel material. It has an easy-access magazine release and a last-round bolt hold-open feature. However, it does need a Glock cut bolt to install, and you might need to shave a little off the ejector for it to work.

Hahn Precision AR-15 Bottom 9mm Adapter

Best 9mm Conversion Kits Hahn Precision AR-15 Bottom 9mm Adapter
Image source: cdn-bjeckh.nitrocdn.com

The Hahn Precision AR-15 Bottom 9mm Adapter is available in two versions: top loading and a bottom-loading version. The bottom-loading version inserts into the bottom of the receiver. It is secured using a tension feature to prevent it from accidentally coming off. The top-loading version drops in from the top of the lower receiver. It requires you to remove the bolt release to install it.

The Hahn Precision adapter is very durable and made from 6061-T6 billet aluminum and steel. It has a last-round hold-open feature so the bolt will lock to the rear when you fire the last round from the magazine. This block feeds all 9mm ammunition, including self-defense hollow point loads. The adaptor functions well with Colt and Uzi magazines but not with Glock magazines.

Pros
  • Available in top-loading or drop-loading versions
  • Compatible with Colt and Uzi magazines
  • Has a built-in hold open feature on the last round fired
  • Cut for reliable feeding with hollow point rounds
Cons
  • Not compatible with Glock magazines

The Hahn Precision adapter is a solid choice for a 9mm AR-15 conversion kit as long as you are using Colt or Uzi magazines. It is available in a top-loading or bottom-loading format. It also comes with a last-round hold-open feature and can function well with hollow point ammunition.

Rock River Arms AR-15 9mm Magwell Conversion Block

Best 9mm Conversion Kits Rock River Arms AR-15 9mm Magwell Conversion Block
Image source: cdn-bjeckh.nitrocdn.com

The Rock River Arms AR-15 9mm Magwell Conversion Block is designed for Colt- and Uzi-style magazines. It will lock to the rear with Colt magazines, but not when using Uzi magazines. Additionally, it won’t work with Glock-style magazines.

Rock River Arms made this conversion block out of durable steel and aluminum. In addition, it’s built with MIL-Spec standards. It has a bottom-loading design that uses a set screw to get the magazine block secured to your AR-15. This enables you to use the standard magazine catch on your AR-15 rather than installing a new one.

Pros
  • Built out of durable steel and aircraft-grade aluminum
  • Built to MIL-Spec standards
  • Designed to function with Colt and Uzi magazines
  • Allows you to use the standard magazine catch on your AR-15
Cons
  • Not compatible with Glock magazines
  • Does not lock open on Uzi magazines but will with Colt magazines

The Rock River Arms conversion block is a good choice if you want a durable and high-quality MIL-Spec-grade 9mm conversion kit. It’s designed in such a way so that you can use the standard magazine catch on your AR-15. It is fully compatible with Colt and Uzi magazines.

The Rock River Arms conversion block is a good choice if you want a durable and high-quality MIL-Spec-grade 9mm conversion kit. It’s designed in such a way so that you can use the standard magazine catch on your AR-15. It is fully compatible with Colt and Uzi magazines.

Conclusion

That concludes our list of the top three best 9mm conversion kits for 2021. Any of these will be a solid option for converting your AR-15 from its current rifle caliber configuration into a 9mm version. Make sure that you identify from the start what type of magazine you are planning on using. You can also follow the buyer’s guide we set up to find a different high-quality model.

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