SIG Sauer M400 SDI X-Series 5.56 NATO 16in 30rd
About this product
The SIG Sauer M400 SDI X-Series is a purpose-built modern sporting rifle chambered in .223 Rem/5.56 NATO with a 16-inch chrome moly barrel and a mid-length gas system for balanced cycling. The X-Series receiver set adds precision machining and ambidextrous controls, while the free-floating handguard supports modular accessory mounting. It ships with a single 30-round polymer magazine and a Magpul SL-style telescoping stock for adjustable ergonomics.
Key Specifications
- The caliber is .223 Rem/5.56 NATO.
- The barrel measures 16 inches.
- The barrel material is Chrome Moly Steel.
- The handguard is a 15″ free-float M-LOK design.
- The twist rate is 1:7.
- The trigger is a SIG Flatblade Match unit.
- The stock is a Magpul SL-K 6-position telescoping configuration.
- Included magazine configuration is 1 × 30‑round polymer magazine.
- The muzzle device is a hybrid compensator/flash hider.
- The unloaded weight is approximately 7.0 lb.
Engineered for dependable out-of-the-box performance, the M400 SDI X-Series pairs proven materials and ergonomics with a modular M-LOK fore-end and a match-style trigger to support accurate, repeatable shooting at the range or in training. Its combination of a mid-length gas system, precision-machined receiver, and accessory-ready handguard makes it a practical choice for shooters who value durability, control, and straightforward functionality.
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Specs at a glance
Key attributes
| upc | 798681664634 |
| manufacturer | SIG SAUER |
| manufacturer part number | RM400-SDI-16B-P |
| action | Semi-Auto |
| atf type | MODERN SPORTING RIFLE |
| barrel finish | Black FNC |
| barrel length | 16'' |
| caliber/gauge | .223 REM/5.56 NATO |
| capacity | 30 |
| color | Black |
| length | 36.8'' |
| magazine included | 1 x 30-Round |
| model | M400 |
| number of magazines | 1 30 rd. |
| package height | 4.3 |
| package width | 11.3 |
| product type | AR |
| safety | AMBI SAFETY CONTROL |
| shipping weight | 10.0 |
| sights | No |
| state restriction (ca) | NO DIRECT SHIP TO CALIFORNIA |
| state restriction (ri) | NO DIRECT SHIP TO RHODE ISLAND |
| state restriction (wa) | NO DIRECT SHIP TO WASHINGTON |
| thread pattern | 1/2"-28 tpi |
| units per box | 1 |