Stern Defense SD Mod 4 9mm AR-15 Upper Receiver

Feb 9, 2019 | 9mm AR15 Upper Receiver

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Picture of a Stern Defense SD Mod 4 9mm AR-15 Upper Receiver

Stern Defense SD Mod 4 9mm AR-15 Upper Receiver

I noticed the SD Mod 4 9mm AR-15 Upper Receiver on Brownells new product section so I spent a bit of time researching Stern Defense. I didn’t learn much. The only thing I was able to determine besides their contact information is that they are a pistol caliber AR-15 hardware manufacturer, and as regular visitors know we are big proponents of the platform. If anyone has feedback on the hardware or company please drop us a line!

The Stern Defense SD Mod 4 9mm Upper Receiver is a complete, ready to go, upper receiver solution for those looking to spend less time building and more time shooting.

The 4 inch, 1-10 twist, Melonite finish barrel, is free float in a 4in M-LOK handguard attached to a 7075-T6 forged aluminum receiver.
On the end of the barrel mounted on the ½-36 threads is a 1.75” long, 1.2” diameter blast can designed to direct the short barreled blast away from the shooter.

  • 4in barrel
  • 4in M-LOK Free Float handguard
  • Complete assembly with 9mm bolt and charging handle
  • ½-36 muzzle thread pitch
  • 1.75” long by 1.2” diameter blast can muzzle device
  • SD BU9 9mm Bolt
  • Cartridge: 9mm Nato

Included in the upper receiver is charging handle and the Stern Defense 9mm Bolt which is compatible with both Glock and Colt SMG magazines, has a Melonite finish, and is works in conjunction with the Law Tactical Folding Adapter. The Stern Defense SD Mod 4 9mm Upper Receiver is made in the U.S.A

Stern Defense 4 inch MLOK rail(Barrel nut, bolts etc.)
Stern Defense 4 inch 9mm barrel.
SD MBC 9MM Blast Can.
Stern Defense assembled upper receiver with dust cover and forward assist.
Stern Defense SD BU9 Glock cut bolt.
SD CH1 enhanced charging handle.


The free float MLOK handguard from Stern Defense offers excellent ergonomics while remaining lightweight and strong. This handguard is MLOK compatible to accept your favorite attachments. Features a secure clamp on mounting system that ensures that the handguard remains in place even under heavy abuse, sustained full auto fire, and shooting prone from a bipod. Machined from 6061 aircraft grade aluminum and hard-coat anodized for longevity and durability. These handguards also feature quick disconnect swivel holes.  Also Included,  Barrel Nut and Bolts.

  • 6061 aircraft grade aluminum.
  • Hard-coat anodized.
  • Sturdy construction.
  • Lightweight construction.
  • Length 4 inches.
  • Smallest inside diameter 1.435 inches.
  • Made in U.S.A.

9mm Barrel

Stern 9mm barrels are ideal for gun lovers who want to build their own custom dedicated 9mm AR15 upper group. Our barrels offer an advantage over the competition. Every stern defense barrel throat is machined deeper for a longer free bore to accommodate bullets with a longer ogive. We have found that some common defense rounds jam into the rifling before the round is fully chambered. Some of the barrels on the market do not accommodate this and will potentially result in nasty malfunctions, resulting in a round being stuck in the chamber requiring manual methods to clear the malfunction.

Note: Barrel comes with locating pin installed.

  • Barrel length is measured in overall length from breech to muzzle.
  • Caliber: 9mm.
  • Length: 4 Inches.
  • Made in the U.S.A.
  • Threaded .5-36.
  • 1:10 TWIST.
  • 4150 Chrome-moly steel.
  • Melonite coating.

9mm Receiver

Mil-Spec flat top upper receiver with Stern Defense laser engraved dust cover and forward assist. Machined from 7075-t6 aluminum and hard-coat anodized. Mil-spec dry film lube in the bore.

  • 7075-t6 aluminum
  •  Hard-coat anodized.
  •  Sturdy construction.
  •  Made in U.S.A.

9mm Charging Handle

Mil-spec charge handle for AR-15 rifles.  Laser engraved with Stern Defense logo.  Our latch is  Ergonomically designed and provides a positive grip and easy one hand manipulations while charging your weapon under stressful situations. Made from 6061 aircraft grade aluminum billet and hardcoat anodized.

  • Laser engraved.
  • 6061 aircraft grade aluminum billet
  • Hard coat anodized.
  • Sturdy Construction.
  • Made in U.S.A.

9mm Specific Bolt

Made with 8620 AISI steel and boasting a Mag-Phosphate finish, the Stern bolt fits into Mil-Spec and Glock-pattern upper receivers.  It functions with Colt SMG, Glock magazines and it’s fully compatible with standard AR15/M16 charging handles. Comes fully assembled with all sub-components installed, including firing pin/spring/retaining pin, extractor, and extractor spring.   Also included in bolt assembly is a proprietary center and roll pins.  Our 9mm bolts incorporate our new bolt design which caters to single stage triggers with short resets.  It also allows use with the JP silent captured spring. This bolt is compatible with the Law Tactical folding stock and the Echo trigger.

  •     Made in U.S.A.
  •     Constructed from 8620 AISI steel.
  •     Custom 4140 billet extractor providing superior ejection.
  •     Glock cut.
  •     Coating: Mag-Phosphate
  •     Weight: 15.5 OZ with weight 13.3 OZ without..
  •     9mm
  •     Compatible with single stage short reset triggers.
  •     Compatible with the Law Folding Tactical Stock
  •     Compatible with the Echo trigger.
  •     Compatible with the JP Silent capture spring

9mm Blast Can

Designed to direct muzzle blast away from shooters. Which is especially helpful on short barreled rifles and pistols. Machined from 6061 aircraft grade aluminum billet and hardcoat anodized, 1.75 inches long and 1.2 inches in diameter.

Note:  Comes with crush washer.

  • 6061 aircraft grade aluminum.
  • Hard-coat anodized.
  • Sturdy construction.
  • Lightweight construction.
  • Made in U.S.A.
  • 9mm
  • Threaded .5-36

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