SIG SAUER M400 TREAD 5.56 NATO Semi-Auto Rifle, 16 in Stainless Barrel, Mid-Length Gas, Free-Float M-LOK, 4x 30-Rd Mags
This SIG SAUER M400 TREAD is a 5.56 NATO AR-15 platform rifle built around a 16-inch stainless, free-floating, threaded barrel with a 1:8 twist and a mid-length gas system. It features a flat-top upper with T-marked Picatinny rail, forward assist, and ejection-port dust cover, plus a free-float aluminum M-LOK TREAD handguard with TREAD logos. It comes with four 30-round Magpul PMAGs and the SIG SAUER factory box labeled M400-16B-TRD dated 10-JAN-2023.
Condition
Overall Condition: Very good condition, showing only light, superficial signs of prior handling or use.
Bore Condition: Excellent - Clean, mirror finish, no signs of wear.
Bore Rifling: Excellent Rifling - Sharp lands and grooves.
Specific Condition Notes: This rifle is in great shape with minimal wear. There are a few small scuffs and scratches from prior handling.
What’s Included
- SIG SAUER factory box with M400-16B-TRD label
- Four 30-round Magpul PMAG polymer AR-15 magazines
The stainless, 16-inch barrel is free-floating and threaded at the muzzle, capped with an open-prong flash hider. A 1:8 twist supports a broad range of 5.56 NATO and .223 Remington bullet weights, and the mid-length gas system with a low-profile gas block is paired with a direct-impingement, rotating-bolt action.
The flat-top upper receiver carries a T-marked Picatinny rail for mounting, and includes a forward assist and an ejection-port dust cover. This upper shows a recognized keyhole forge mark. The lower and upper are aluminum, matching the rifle’s lightweight AR-15 configuration.
Up front, the free-float aluminum M-LOK TREAD handguard uses a two-screw clamp and displays TREAD logos. The rifle retains standard rail real estate while keeping the handguard slim for accessory placement along the M-LOK slots.
The stock is a telescoping, adjustable polymer unit with a listed 13.0-inch length of pull, and it is matched to a SIG SAUER textured polymer pistol grip. Capacity is 30+1, and this example includes four 30-round PMAGs. The factory box label date is 10-JAN-2023, and the rifle is marked as made in the USA. The manufacturer’s part number is M400-16B-TRD.