The NEMO Omen Mongoose is a 9mm AR-pattern pistol with a 5.8-inch steel barrel threaded 1/2x28. An SB Tactical FS1913 brace is mounted at the rear, giving it a pistol-caliber-carbine-style shooting stance while it stays classified as a pistol. The gun runs a short-recoil operating system and includes a 35-round magazine. 
 

Key Specifications 

• Brand: NEMO 
• Model: Omen Mongoose 
• Caliber: 9mm 
• Action: Semi Auto 
• Barrel Length: 5.8 in 
• Capacity: 35-round magazine included 
• Finish: QPQ Nitride 
   

Detailed Features 

• The barrel is threaded 1/2x28 for a suppressor or muzzle device. 
• An SB Tactical FS1913 brace is fitted for a compact PCC-style shooting stance. 
• The upper carries a Picatinny top rail, and the handguard is M-LOK compatible for optics and accessories. 
• The safety selector and bolt catch/release are both ambidextrous. 
• It ships with a Magpul MOE SL grip and a 35-round Magpul PMAG 35 EV9, a CZ Scorpion-pattern magazine.

Owners of AR-pattern 9mm pistols like the Omen Mongoose generally like that NEMO builds it on a well-supported operating platform rather than a proprietary design, which keeps parts and support easier to find. The QPQ nitride finish on this model gets called out favorably for corrosion resistance on a gun that sees a lot of handling.

Ergonomically, the brace and the M-LOK handguard let owners set the gun up close to how they run a full-size carbine, and that carryover in controls is a common point of praise. The ambidextrous safety and bolt release matter to left-handed shooters specifically, since braced pistols in this category don't always include them.

On value, buyers weigh the Mongoose against other 9mm AR pistols and note the barrel comes already threaded, which is one less aftermarket part to buy. Because it runs a CZ Scorpion-pattern magazine, owners also find spare magazines and aftermarket parts are easy to source.