The M400 X-series features a free-floating M-LOK handguard, Magpul SL-K 6-position telescoping stock, Sig Flat Match Grade trigger, 16" Chrome Moly barrel, and a 7075 T-6 aluminum receiver with a black hardcoat anodized finish.
| Barrel Description | Chrome Moly Steel |
| OAL | 33.50"- 36.75" |
| FireArm | yes |
| Safety | Ambidextrous |
| Caliber | 5.56x45mm |
| Weight | 7 lbs |
| Muzzle | Hybrid Compensator/Flash Hider |
| Action | Semi-Auto |
| Weight Range | 7 lbs to 7.99 lbs |
| Hand | Right Hand |
| Stock Finish Group | Black |
| Stock Description | Magpul SL-K |
| Barrel Length | 16" |
| Receiver Material | Aluminum |
| Twist | 1:7" |
| Barrel Length Range | 16" to 16.99" |
| Trigger | Flatblade Match |
| Capacity | 30+1 |
| Sights | Optic Ready |
