The Sig Sauer P320 Flux is a striker-fired 9mm pistol built on SIG's modular fire control unit and paired with a polymer Flux chassis. It has a 5.5-inch threaded barrel (1/2x28), a non-reciprocating Picatinny optic mount cut into the slide, and ships with a stabilizing brace. The package includes four steel magazines, two 30-round and two 21-round. 
 

Key Specifications 

• Brand: Sig Sauer 
• Model: P320 Flux 
• Caliber: 9mm Luger 
• Action: Striker-Fired Semi-Auto 
• Capacity: 21+1 / 30+1 
• Barrel Length: 5.5" 
• Weight: 49.2 oz (with one magazine) 
• Finish: Nitron 
   

Detailed Features 

• 1/2x28 threaded barrel accepts standard muzzle devices. 
• Non-reciprocating Picatinny rail lets an optic mount directly to the slide. 
• SIG X-RAY 3 day/night sights stay on the slide for backup use with an optic. 
• Ambidextrous dual magazine release and an integrated flared magwell speed up reloads. 
• Rapid-deploying stabilizing brace is installed for a compact, braced setup.

Owners of the P320 line generally trust the fire control unit to run reliably, and that reputation carries over to the Flux configuration. The stainless steel slide and FCU feel more substantial than lighter polymer-slide pistols, and the Nitron finish holds up to regular handling.

Opinions on the brace setup are mixed. Some shooters like having a compact, braced P320 for truck-gun or range duty, while others find the added length and brace bulk make it holster more like a large pistol than a typical carry gun. The ambidextrous magazine release and flared magwell draw consistent praise for making reloads faster under pressure.

Because the Flux shares its fire control unit with the rest of the P320 family, it benefits from that platform's wide aftermarket: grip modules, sights, and holsters are easy to source. Buyers who wanted a braced 9mm with extra magazines see real value in the bundle, though a few owners note the threaded barrel and brace add setup steps compared to a standard P320.