Use Sig-P320 Ammo In Your AR-15? Yes, With This Adapter

Image courtesy of Matador Arms.

There is something to be said for having many options when it comes to weapons and ammunition, but, if you’re like most people, it’s unlikely that you’ll have the financial means to buy literally every firearm in every ammo option that is available someplace. This means, of course, having to buy smart and make the most of your options.

Fortunately, though, you can sometimes “create” options without having to buy every single model of firearm. For example, Matador Arms has released an adapter for your AR-15 allowing you to use Sig-P320 ammunition in that rifle. Just so you have more options. Duncan Johnson writes,

The Mag-X allows the use of Sig-P320 pistol magazines in any AR-15 milspec lower receiver. No modifications are required to the lower or the magazine, and the Mag-X installs in seconds, enabling the use of Sig-P320 magazines. The Mag-X has a built-in magazine release and locks into place with the standard AR-15 catch. It is manufactured from aircraft-grade aluminum and has an anodized finish. The ejector and magazine catch are both steel.

The Mag-X is available for sale in both the United States and Canada. Made in Canada, the Mag-X ships to USA customers direct from Matador’s USA warehouse. MSRP is $149.99 USD, with special introductory pricing available for those who want to jump on this.

Matador Arms themselves gives us a few more details:

  • Fits any standard AR-15 lower receiver.
  • No modifications required to your lower or magazine.
  • Installs in seconds, enabling use of Sig-P320 magazines.
  • Built-in magazine release for Sig-P320 style magazines.
  • Locks into place with the standard AR-15 catch.
  • Lightweight aircraft-grade aluminum construction; anodized finish.
  • Steel ejector and magazine catch.
  • Only compatible with mil-spec AR-15 lower receivers, combined with a 9mm upper with a Glock-cut bolt.
  • No last round bolt hold open.

So, if you only want to buy one type of ammunition (Sig P320, in this case) an adapter can give you some options in what you’re using that ammo. If you’re that person, then give this adapter a look.



  1. I’m confused. Your saying 9mm ammo can be run through an AR-15? How is that possible when an AR-15 takes a .223 or 5.56 NATO?

    • Yes. It was a poorly worded article, but you can get 9mm uppers for AR15s. They have been available for a long time, but up until recently, used proprietary magazines. With the increasing popularity of pistol caliber carbines (PCC’s), there are many models now that use popular pistol magazines, usually Glock. More manufacturers now are making lowers, or adapters, for other common brands. This way you can have magazine commonality between your carbine and sidearm.

  2. I think if you read it more closely it says you need a 9mm upper. Then your buying an adapter to go into ar15 magwell with a 320 magazine.

  3. It gets rather expensive if you have to buy a 9mm upper. I was excited at first, but now it is not cost effective. Not to mention the time it takes to switch back and forth.

  4. The article could have been a little more clear and mention you must have a 9mm UPPER but they DID specify the compatibility with the AR15 LOWER. PCC’s are attractive, particularity if you are going to “Tenzing Norgay” a lot of ammo (not to mention $’s savings for ammo). So a 9mm upper is an attractive option. Of course, the inexpensive way to do that is to purchase the 22Long adapter & mag (works with AR15 upper & lower) but the 9mm option packs more of a punch -that’s a good thing. …so many options, so little time!

  5. It also says along with the 9mm upper and the $150 dollar mag x,and 9mm ammo, spare clips, the ar upper will also need a Glock cut bolt . At that price tag I know of two really good carbines you could purchase at and have higher magazine capacity like 33 rounds, hint hint. Unless I read it wrong,if so please correct me , because the math just dont add up. Unless they drop the price on the mag x to @ $50 bucks and you own a sig already.

  6. Oh yeah, I forgot one last thing. Also, you have to guess if you have a battery jam or if your out of ammo, or if you had a bad primer that didn’t fire because there is no nill bolt catch excuse me no last round bolt catch hold open.

  7. Don’t forget to buy a new upper and barrel chambered for 9mm. May as well just call PSA and buy a AR chambered for 9mm already, lot cheaper in the long run!!!

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