SIG Sauer M400 TREAD 5.56 NATO AR-15, 16 in Stainless Barrel, Mid-Length Gas, 1/8 Twist, Threaded 1/2x28, Free-Float M-LOK
This SIG Sauer M400 TREAD stands out as a feature-rich, AR-15–platform rifle with a 16 in stainless, threaded barrel, a mid-length gas system, and a slim free-float M-LOK handguard. It comes in excellent overall condition with a clean, mirror-finish bore, and includes the factory box and a 30-round Magpul PMAG. The box label is dated 12-Nov-2022 and matches the receiver.
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 Rifling - Sharp lands and grooves.
Specific Condition Notes: This rifle shows little prior use. The bore is clean and shiny.
What’s Included
- SIG Sauer factory cardboard box with RM400-16B-TRD label
- One 30-round Magpul PMAG polymer AR-15 magazine
The M400 TREAD uses a mid-length gas system with a low-profile gas block, paired to a 16 in stainless steel barrel with a 1/8 twist for broad bullet compatibility. The barrel is threaded 1/2-28 UNEF and fitted with a three-prong flash hider.
Forged aluminum receivers with a hard-coat anodized finish anchor the build. The upper features a MIL-STD-1913 Picatinny rail with T-marked slots, plus a forward assist and an ejection port cover. A slim, approximately 15 in free-float aluminum M-LOK handguard with the TREAD logo provides direct accessory mounting.
Furniture includes a 6-position adjustable polymer stock and a SIG-branded polymer pistol grip with textured panels. Controls are straightforward, with a manual safety selector showing pictogram SAFE/FIRE markings and a single-stage trigger.
Overall length runs approximately 32.6–35.8 in and the unloaded weight is about 7.0 lb. This rifle is chambered in 5.56mm NATO with a 30+1 capacity. It is the RM400-16B-TRD configuration, made in the USA, and the box serial matches the receiver.