The Sig Sauer SIGM400 SDI X is a modern 5.56 NATO rifle built for shooters who demand reliability and precision without compromise. Whether you're training at the range, hunting, or setting up for duty-style shooting, this direct impingement rifle pairs Sig's reputation for quality with a pedigree of real-world performance. The 16-inch cold hammer forged steel barrel is threaded for suppressors or other muzzle devices, and the mid-length gas system strikes a balance between reliability and controllability across standard ammunition.
What sets the SDI X apart is the attention to ergonomics and shooter control. The rifle ships with fully ambidextrous controls, so lefties and righties operate the same platform without compromise. The SIG 2-Stage Matchlite Duo trigger delivers a clean, predictable break—no creep, no surprise—making follow-up shots faster and more accurate. The low-profile gas block sits low enough to pair cleanly with optics, and the integrated SIG flash hider-compensator manages both muzzle flash and recoil impulse in one compact package.
The M-LOK handguard gives you plenty of real estate for lights, grips, and accessories, and the 6-position Magpul MOE-SL stock lets you dial in length of pull for your body and gear. Finished in FDE Cerakote, the rifle handles hard use without showing every scratch. At just over 7 pounds loaded, it's light enough for a long day in the field but substantial enough to run smoothly through rapid strings. One 30-round magazine is included.
| Caliber | 5.56 NATO |
| Barrel Length | 16 inches |
| Barrel Material | Cold hammer forged steel |
| Barrel Finish | FNC |
| Barrel Twist | 1:7 inch |
| Barrel Threading | Threaded |
| Gas System | Mid-length direct impingement |
| Handguard | M-LOK |
| Trigger | SIG 2-Stage Matchlite Duo |
| Stock | 6-position Magpul MOE-SL |
| Muzzle Device | SIG flash hider-compensator |
| Frame Material | Alloy |
| Frame Finish | FDE Cerakote |
| Magazine Capacity | 30 rounds |
| Controls | Fully ambidextrous |
| Overall Length | 36.5 inches |
| Overall Height | 7.1 inches |
| Overall Width | 2.75 inches |
| Weight (with magazine) | 7.0 pounds |
| Includes | One 30-round magazine |
Yes. The rifle features fully ambidextrous controls, making it equally comfortable for left- and right-handed shooters without any modifications or switch kits.
Yes. The 16-inch barrel is threaded, allowing you to attach a suppressor, muzzle brake, or other threaded muzzle devices that are legal in your jurisdiction.
The SIGM400 SDI X is equipped with a SIG 2-Stage Matchlite Duo trigger, designed to provide a clean, predictable break with minimal creep.
The rifle ships with one 30-round magazine. No additional accessories are included with this model.
Sig Sauer
ATI Ammunition
ATI Ammunition
Sig Sauer
