SIG Sauer M400 TREAD 5.56 NATO AR-15 Rifle, 16 in Stainless Threaded Barrel, Mid-Length Gas, Free-Float M-LOK, Ambi Controls, Red Dot Installed
This SIG Sauer M400 TREAD stands out as a well-configured 5.56 NATO AR-platform rifle with a 16-inch stainless, threaded barrel and a mid-length gas system. It features a free-float aluminum M-LOK handguard, ambidextrous controls, and a flat-top Picatinny rail with T-markings. It comes with an open reflex red dot already installed and three Magpul PMAGs, offering a ready-to-use package in very good overall condition.
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 firearm is in great shape overall, with minor surface scratches and small blemishes consistent with light handling.
What's Included
- Open reflex red dot sight (installed)
- 2x 30-round Magpul PMAG polymer AR/M4 magazines
- 1x 20-round Magpul PMAG polymer AR/M4 magazine
- M-LOK rail cover panels installed on handguard
The M400 TREAD uses a 16-inch stainless steel barrel with 1/2x28 UNEF threads and a three-prong flash hider. The 1:8 twist supports a wide range of 5.56 NATO and .223 Remington loads, and the bore presents sharp rifling for consistent performance.
Its mid-length gas system and direct-impingement action pair with a rotating bolt for reliable cycling. The free-float aluminum handguard with M-LOK slots keeps weight down, maintains accessory flexibility, and is fitted with M-LOK rail cover panels.
Controls include an ambidextrous safety selector and ambidextrous magazine release. The rifle features a flat-top Picatinny receiver rail with T-markings, an ejection-port cover, and a forward assist. An open reflex red dot sight is installed for immediate use.
The carbine wears a Magpul-branded adjustable 6-position stock and a SIG-branded polymer pistol grip. Aluminum receivers with a hard-coat finish, overall length of 32.6–35.8 inches, and an unloaded weight around 7 lb round out a balanced, USA-made package that is part of SIG's TREAD accessory ecosystem. Capacity is 30+1, and three PMAGs are included.