Sig Sauer M400 Enhanced 5.56mm NATO AR-15 Rifle | 16" Chrome-Lined Barrel, Magpul Furniture, MBUS Sights
The Sig Sauer M400 Enhanced is a factory-upgraded AR-15 that pairs Sig’s forged 7075-T6 receivers with Magpul MOE furniture and MBUS flip-up sights. This discontinued variant delivers a chrome-lined, 16-inch 4140 CMV barrel threaded 1/2x28, a 1:7 twist optimized for heavier 62–77 grain loads, and integral QD sling cups machined into the lower receiver. All components remain in excellent condition, showing only minimal evidence of prior handling.
Condition
Overall Condition: Excellent condition, showing only faint signs of any prior use or handling.
Bore Condition: Excellent - Clean, mirror finish, no signs of wear.
Bore Rifling: Excellent - Sharp lands and grooves.
Specific Condition Notes: Minimal markings from previous handling and use; bore is bright and clean.
What’s Included
- Sig Sauer M400 Enhanced 5.56mm semi-automatic rifle with factory Magpul MBUS flip-up sights
- One 30-round Magpul PMAG polymer magazine
The Enhanced package equips the M400 with Magpul MOE carbine-length handguard, six-position stock in OD/FDE, and a matching MOE pistol grip, giving the rifle a ready-to-run setup straight from the factory.
Its 16-inch, chrome-lined barrel is cut from 4140 CMV steel for durability and heat resistance, while the 1:7 right-hand twist stabilizes heavier projectiles commonly used for defensive or match purposes.
The forged 7075-T6 upper and lower receivers feature a hard-coat anodized finish, a properly staked carrier key, and built-in QD sling cups—details that underscore Sig’s attention to long-term reliability.
This model retains standard AR-15 controls, a direct-impingement gas system, and a 1/2x28 threaded muzzle for flash hiders, brakes, or suppressor mounts.
Phased out before the current TREAD series, the M400 Enhanced is no longer in production, making clean examples such as this attractive to shooters and Sig Sauer collectors alike.