How to Convert an AR-15 to 9mm: The Best AR 15 9mm Conversion Kit

Last Updated on January 5, 2021.

9mm carbines are excellent guns. And shooting 9mm from an AR-15 platform is the simplest way to transition to a pistol caliber carbine, because the controls and weapon manipulations are the same as an AR-15.

Also, a 9mm AR-15 is ridiculously fun to shoot. And shooting 9mm is more affordable than shooting 5.56mm.

The most affordable way to get a 9mm AR-15 is to convert a 5.56mm AR-15 to 9mm using an AR-15 9mm conversion kit.

Now here’s the deal with AR-15 9mm conversion kits: there aren’t any prebuilt kits. To convert your AR-15 to 9mm, you’ll essentially need to build a 9mm upper receiver and find a way to put 9mm magazines in your lower receiver.

If you have a .223 or 5.56mm AR-15, you already have the upper and lower receiver. So, here are the parts you’ll need to build the Minuteman Review best AR-15 9mm conversion kit:

Our Best Choice

These three parts will get you a fully functioning 9mm AR-15 for a reasonable price. And a PCC built with these parts will last for a long time and operate reliably.

If you want to see the other options, so you can mix and match parts for the best deal or most custom build, keep reading. We’ve put together a few kits that will get you shooting 9mm from your AR-15 quickly and affordably.

Top AR 15 9mm Conversion Kit on the Market Today

Best AR 15 9mm Conversion Kit Reviews: Shooting Pistol Bullets from Your Rifle

Our overall best AR 15 9mm conversion kit is up first. The other best AR 15 9mm conversion kits will be presented in order of price.

Most affordable kits first.

Most expensive kits last.

Simple as that. Let’s see what we can put together.

1. Faxon Firearms and Hahn Precision Combo - Overall Best AR-15 9mm Conversion Kit

Faxon Firearms barrels have been my go-to for affordable AR-15 barrels for a while now. They make quality equipment. Conveniently, they also make a 9mm bolt carrier group that goes nicely with their barrels.

Here’s the Minuteman Review choice for the best combo of parts to convert your AR-15 to 9mm (and why we think this is the best way to go):

First, the Faxon Firearms barrel is a solid all-around barrel. It’s an excellent barrel for the money. And it comes in 8.5 inches, which is a nice all-around PCC barrel length.

Or you can get the 16-inch model, if you’d rather not pay for the SBR tax stamp or if you need to meet length requirements for competition.

The Faxon Firearms bolt carrier group isn’t the least expensive bolt carrier group on the market. But it’s easily one of the best. The main reason is that this bolt carrier group works with standard AR-15 parts.

No modified 9mm upper receiver. No heavy buffer. Just put it in your upper receiver, and it works. It’s a simple, reliable, and affordable bolt carrier that’s pretty much guaranteed to match up with a Faxon 9mm barrel.

Lastly, the Hahn Precision conversion block. It’s also simple. No lower receiver modification required. And it retains all the standard AR-15 controls. So you don’t need to learn new weapon manipulations.

Also, this conversion block takes Colt 9mm magazines, which are the best 9mm carbine magazines. They lock up securely, with very little wobble. That gives you the most reliability.

This isn’t the least expensive AR-15 9mm conversion kit. However, it definitely gives you the most bang for your buck.


  • Works with standard AR-15 upper and lower receivers. No modification necessary.
  • Retains all the standard AR-15 controls, so you don’t need to learn any new firearm manipulations.
  • Uses Colt magazines for maximum reliability.


  • There are less expensive options.

2. Brownells, Ballistic Advantage, and Rock River Arms Combo - Budget AR-15 9mm Conversion Kit

This combo is slightly less cohesive than our overall best 9mm conversion kit. But it’s a tad more affordable. And it works just as well. Here’s what you get:

The Brownells 9mm bolt carrier group is less expensive than some of the alternatives. But not much less expensive. You save a few bucks without compromising on quality. It’s machined from a single piece of tool steel. And it works with standard AR-15 upper receivers.

Some shooters have reported that this bolt carrier group requires a heavier buffer, despite being a full-mass bolt carrier group. You may need to get a dedicated buffer for your 9mm carbine. But it’s an inexpensive part.

Even so, you get the reliability and simplicity you need at a bit of a discount. Not a bad deal.

Ballistic Advantage barrels are probably the best budget barrels out there. There may not be any barrels that offer the same quality for the money. And you can get these barrels in 5.5, 8.3, or 16 inches, depending on what you need.

The only downside is that this barrel has more limited conversion block compatibility than some other barrels.

Which brings us to the Colt dedicated conversion block. It retains your standard AR-15 controls and firearm manipulations. And it takes Colt 9mm magazines (obviously. Why would colt make a conversion block that takes someone else’s magazines?).

So it keeps your 9mm carbine simple to operate and reliable.

The downside to this conversion block is that it’s not a drop-in installation. You’ll need to punch a couple pins to get it installed. However, once it’s installed, it’s super secure. It’s just not as easy to convert your lower receiver back to 5.56mm.

However it’s significantly less expensive than most drop-in conversion blocks. When you couple that with the lower price of the barrel and bolt carrier group, this kit is a remarkably affordable way to start shooting 9mm from your AR-15.


  • Works with standard AR-15 upper and lower receivers.
  • Uses all the standard AR-15 controls. No need to learn new firearm manipulations.
  • Most affordable option.


  • Barrel may not be compatible with different conversion blocks.
  • Conversion block requires some tools to install.

3. CMMG, Angstadt Arms, and Brownells Combo - Value AR-15 9mm conversion kit

CMMG is one of the leaders in AR-15 9mm conversions. They were one of the earliest manufacturers of complete 9mm AR-15 carbines. And their parts are extremely well made. So it makes sense that you’d pair CMMG internals with a slightly pricier barrel.

Here’s the 9mm conversion kit:

The CMMG bolt carrier's claim to fame is that it’s built to mil-spec standards for rifle rounds in terms of steel, staking, etc. So it’s more than durable enough to handle 9mm rounds.

It’s also compatible with both Glock and Colt magazines. This is handy if you want to use the same magazines in your carbine as you use in your handgun (use the Stern Defense conversion block for this). Colt 9mm magazines can be pricey. So using Glock magazines could save you some money.

Unfortunately, since CMMG is so dedicated to mil-spec standards, this bolt carrier group is phosphate coated. The finish is perfectly durable and the performance is fine. Most people won’t notice the difference. But a nitride coating would be nice for the price.

The barrel is a bit fancier than some of the other options. The main benefit of this barrel is that it’s a lightweight profile barrel. If you use a shorter barrel, you’ll get a remarkably lightweight pistol caliber AR-15. But the precision is still top-notch.

Last bit: the conversion block. The Brownells conversion block is essentially a standard conversion block. The block itself is easy to install and requires no modification of your lower receiver.

You also keep all your standard AR-15 controls. That way you have no need to change up your firearm manipulations.

But—and this is a bigger deal than you might think—this comes with a Colt 9mm carbine magazine.

Colt 9mm magazines are kind of expensive. So getting a magazine with your AR-15 9mm conversion kit not only means you’re ready to go to the range as soon as your PCC is assembled, it also makes this conversion kit more affordable, overall.

That’s why this is such a great value kit. The performance is solid. But it won’t quite blast your budget.


  • Bolt carrier group is built to rifle-caliber standards. So it’s exceptionally durable.
  • Lightweight barrel makes your pistol caliber carbine nice and light.
  • Conversion block requires no modification of your lower receiver and retains all of your standard AR-15 controls.
  • Includes a Colt 9mm magazine.


  • Bolt carrier group is phosphate coated. Nitride coating would be nice for the price.
  • Barrel only comes in 4.5 and 10.5-inch lengths.

4. Foxtrot Mike Products AR-15 9mm Upper Receiver and Stern Defense AR-15 9mm Conversion Adapter - Complete Upper Receiver AR-15 9mm Conversion Kit

Maybe you’re not into swapping out your barrel and bolt carrier and whatnot. The Foxtrot Mike Products AR-15 9mm Upper Receiver eliminates all the assembly and disassembly. Just slap the upper receiver on your lower receiver and go.

The two big things about this upper receiver are the magazine compatibility and the finish.

The upper receiver—including the bolt and bolt carrier—is almost entirely finished in black melonite, which is durable and reduces wear on the internal parts. This upper receiver delivers excellent lifespan and performance, especially when you consider the price.

Then, this upper receiver is compatible with Glock magazines. Glock magazines are some of the most affordable 9mm magazines you can use for your PCC. And, if you own a Glock, you probably already have the magazines you need.

That’s what the Stern Defense AR-15 9mm Conversion Adapter is for. It enables your lower receiver to accept Glock magazines.

This adaptor is easier to install or remove than any other conversion block. And it keeps the controls similar to standard AR-15 controls. The magazine release isn’t exactly the same. But it’s fairly close. So the learning curve is easy.

However, the magazine catch interface on Glock magazines doesn’t lock super tightly into the lower receiver. There’s a tad bit of wobble which can cause very occasional malfunctions, even with the adapter.

But, using a complete upper receiver that takes Glock magazines is the fastest and easiest way to convert your 5.56mm AR-15 into a pistol caliber carbine without hassling with changing out barrels and swapping bolt carriers. And that's definitely a dependable tool.


  • Upper receiver comes completely assembled. All you have to do is put it on a lower receiver.
  • Upper receiver is completely finished with black melonite—including the bolt carrier.
  • Accepts Glock magazines.
  • Conversion adapter is incredibly fast and easy to install or remove.
  • Controls are similar to a standard AR-15, though not exact.


  • Glock magazines aren’t quite as reliable as Colt magazines.

Pistol Caliber Fun

When you’re looking at AR-15 9mm conversion kits, what you’re really doing is using your upper receiver as the base for a 9mm bolt and barrel. It takes a bit of work. But you can totally use a single upper receiver to shoot both 9mm and 5.56mm.

Or you could get one of these kits and pair it with an AR-15 upper receiver and charging handle. That way you have a complete 9mm upper receiver that can be hot swapped on a single lower receiver.

There are options. And you can easily mix and match parts from our recommended 9mm conversion kits. But, if you want a solid kit that will make an excellent PCC, put these parts on your upper receiver:

  • Faxon Firearms Gen 2 9mm Bolt Carrier Group.
  • Faxon Firearms 9mm AR-15 Barrel, 8.5 inch.
  • Hahn Precision AR-15/M16 9mm Drop-in Conversion Block.

This kit would make for a really smooth shooting and long lasting 9mm AR-15.

If you haven’t gotten in on the pistol caliber carbine fun yet, it’s time to stop limiting yourself. Put an AR-15 9mm conversion kit together and start shooting more, with less recoil, for less money.