Follow us on Social Media
Image Alt


  /  Firearms   /  Pistol Caliber Carbine   /  Stern Defense Conversion: Pistol Caliber Micro ARs That Use the Magazines You Have

Stern Defense Conversion: Pistol Caliber Micro ARs That Use the Magazines You Have

Stern Defense makes great AR magazine well adapters which turn your AR Lower into a Pistol Caliber Carbine. There are several models available which accept Glock magazines (9mm/.40), Beretta magazines (9mm) and two S&W M&P magazine versions in (9mm/.40 and .45 ACP). The latest version, the MAG-ADMP9&40/P320 , uses both SIG P320 magazines and S&W M&P magazines.

These adapters are very sophisticated. They lock in hard with no wiggle after adjustment. They hold your mags in and drop them free. Unlike some other PCC’s, the bolt hold open works every time.

The .45 caliber adapter uses the excellent S&W M&P magazines.

With the gun ban scares over the last few years and the popularity of 80% lowers, most of you reading this have AR lowers in a closet that you never built. Here is the excuse to build the pistol caliber AR you always wanted. If you only have one AR, in one minute, you can change the upper, buffer and add a magazine well adapter. Boom, new gun.

If you have a registered full auto lower, Stern gives you caliber options. Short Barreled Rifle? Why not blast pistol ammunition? If you have a 9mm suppressor, there is no better host than a 9mm AR. These conversions provide more fun for your training dollar.

This excellent Stern Defense video shows the 9mm kit, installation and full auto firing. I have worked several AR conversions, but there is nothing quite like the Stern Defense system. I got their MAG-AD9 conversion kit, with adapter, complete 9mm caliber upper and their 11 ounce carbine buffer.

The Stern adapter fits snugly into the magazine well and adjust in three axes with Allen head screws. This is what plugs into your magwell. You can see the magazine release sticking out to the left. Photo courtesy of Stern.

Mag-AD series adapters install in seconds, just like an AR magazine. They have a separate magazine release at the bottom you manipulate with your trigger finger and a functioning last round bolt hold open feature. MSRP $186.99

Stern adapters are made of aircraft grade aluminum, lightweight with ergonomic design. There is a tension adjustment feature to eliminate wiggle.

Technical Information:
⦁ Made in the U.S.A.
⦁ Constructed from 6061 T6 aircraft grade aluminum.
⦁ 4140 NiB coated feed ramp.
⦁ Hard coat anodized type 3.
⦁ Sturdy Construction.
⦁ Ergonomic mag release.
⦁ Works with any mil spec ar15 lower receiver.
⦁ All lower components besides the adapter remain stock

Shooting with the Stern P320/M&P adapter using a .40 upper and .40 caliber Lone Wolf upper and a Holosun red dot sight.

Pistol caliber ARs are cheap plinkers and great training tools perfect for new shooters. You can safely shoot handgun steel and use the magazines you already have. Law Enforcement agencies can build an AR that accepts their duty pistol mags for the ultimate police patrol rifle.

Safety Warning:


The big question; Do they work? I have fired over three thousand rounds through four different builds in three different calibers using every kind of ammunition I could find. I have not yet seen a malfunction of any kind. I am still shooting.

I read the instructions and adjusted the three screws. The adapter locked up tight. I oiled the bolt, checked it with a magazine, threw in the 11oz buffer and cycled some dummy rounds. This was too easy, I was wondering if I was doing things right. Everything went right together and cycled perfectly. The Stern adapter fits snugly and it runs smoothly using factory magazines. The magazines drop free and the bolt hold open works.

Stern P320/M&P magazine adapter with a Stern 9mm upper and Nikon P-Tactical SPUR Reflex Sight.

The newest model runs with P320 and M&P magazines in 9mm or .40 S&W. I have tried these in several receivers with multiple uppers. They all ran well with any combination of magazines, uppers and lowers.

The muzzle brake looks great with the flush esthetic that I prefer. It has a conical profile on the inside which effectively focuses the blast forward toward the target

The Stern uppers are the perfect The handguard is light and dissipates heat well.

The recoil is effectively managed with the heavy buffer. I wouldn’t even think about direct blowback with anything lighter. The recoil is more than .223 but less than 12 gauge. It is very manageable and not unpleasant.

Because there is no MILSPEC for pistol caliber ARs, each manufacturer makes them a little differently. If you buy everything from the same place, you chances of an easy build like mine are much higher. Maybe you will be lucky. How ever you decide to get there, now you don’t have to build a dedicated lower. Stern has a web page you can check before purchasing to ensure compatibility with your setup so you don’t buy parts that don’t fit together.

If you are building a gun from parts instead of the Stern conversion kit, there are many parts common to the AR. In addition to a complete lower with an oversized 11 oz buffer, you have to select the correct upper, bolt and barrel to make these guns run.

The Stern Defense bolts are high quality and have the mass to safely and reliably run direct blow back pistol caliber carbines. They look great.

Stern also make a nifty extended polymer magwell that clamps on and speeds up reloads. Photo courtesy of Stern.

Stern Defense makes AR PCCs great again. Stern has all the parts you need to turn your AR Lower into a Pistol Caliber Carbine. There are several versions available which accept Glock magazines (9mm/.40), Beretta magazines (9mm), two S&W M&P magazine versions in (9mm/.40 and .45 ACP). The latest version uses both SIG P320 magazines and S&W M&P magazines.

Want to see their other conversion kits? Click Here.

Bolts? Click Here

Barrels? Click Here

Magwell Adapters Click Here

Stern Defense makes great AR magazine well adapters which turn your AR Lower into a Pistol Caliber Carbine

About Stern Defense:

STERN DEFENSE is a family owned American specialty manufacturer committed to precision, quality, and efficiency of the weapon accessories created. They use the best USA supplied material our products are designed and manufactured by the finest machinists and engineers in the industry.

Stern Defense Magwell Adapters: Turn Your AR Lower into a Pistol Caliber Carbine
The family behind Stern Defense

Their values? Traditional, Rooted, Firm and STERN.

The Stern Family

Featured Photo: The pistol pictured above has the MAG-ADMP9&40/P320 with MOD4 4” M-LOK rail and  4” BARREL 9MM PISTOL UPPER KIT  MSRP $609.46 attached Nikon P-Tactical SPUR Reflex Sight,  GSL Scorpion Suppressor  and SIG Elite Ammunition  Photo by Mark Miller

About the Author /

Mark Miller is a former Customs Agent and a Green Beret who served in Afghanistan and a number of other live fire locations. A student of firearms and shooting, he is an FFL and a SOT. The guiding philosophy of his life is that terrain and situation dictate tactics and the enemy always gets a vote on any plan.

Post a Comment