Description
The P320-FLUX LEGION is a purpose-built chassis system designed to transform your P320 FCU into a high-performance, modular PDW. It’s for the shooter who demands a compact, stable platform for dynamic use, from vehicle-based applications to close-quarters scenarios. Since we started stocking it in spring 2025, it has consistently been one of our top-selling chassis systems, with over 90 units moving through our shop.
Why This One?
- Integrated Brace & Stability: The included Flux FLUX BRACE provides a solid cheek weld and shoulder interface, dramatically improving control and follow-up shot speed over a pistol-only configuration.
- Holster-Ready Design: The chassis features a built-in holster interface compatible with Safariland QLS forks, allowing for rapid transition from a duty belt or chest rig to a deployed, braced firing position.
- Enhanced Modularity: Built on the proven P320 Fire Control Unit, it offers unmatched parts compatibility and customization. The system includes M-LOK slots at the 3, 6, and 9 o’clock positions for lights, lasers, and grips.
- Legion-Grade Build: Manufactured from high-strength polymer with metal reinforcements at critical stress points, it delivers a robust feel without excessive weight. The texturing is aggressive where needed for a secure grip.
- Optimized Balance: The design shifts weight rearward, balancing the system when used with common suppressor-length slides and threaded barrels, reducing muzzle dip and improving handling.
Full Spec Sheet
| Compatibility | SIG Sauer P320 FCU (Full-Size, Compact, Subcompact) |
| Included | FLUX BRACE, Holster Interface, QD Sling Mount |
| Rail System | Integrated Picatinny top rail, M-LOK at 3/6/9 |
| Weight (measured) | 8.0 oz (chassis only, per our scale) |
| Material | High-Strength Polymer with Metal Inserts |
| Color | Black |
| Brace Type | Folding FLUX BRACE |
| Holster Compatibility | Safariland QLS System |
Q & A
Does this work with any P320 slide?
Yes. The P320-FLUX LEGION chassis accepts any standard P320 slide assembly, from subcompact to full-size. The top Picatinny rail provides a consistent zeroing surface for optics, independent of the slide length.
How does it fit different P320 FCU generations?
It fits all generations. Our staff notes a slightly tighter, more precise fit on Gen4 FCU frames compared to Gen5. This is not a functional issue—it simply results in a more solid lock-up with no perceptible play.
Is the brace adjustable?
The FLUX BRACE is a single-position, folding design. Its length is optimized for the chassis geometry to provide a consistent and natural shoulder pocket when deployed. It is not telescoping or length-adjustable.
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