SIG Sauer M400 FORGE 5.56mm NATO, 16 in Cold Hammer-Forged Barrel, Mid-Length Gas, Free-Float M-LOK, ROMEO-MSR Optic
This SIG Sauer M400 FORGE is a factory-configured AR-15 platform rifle in excellent condition, paired with a SIG Sauer ROMEO-MSR micro red dot installed from the optic package. It features a 16 in cold hammer-forged chrome-moly barrel with a 1:7 twist, a mid-length gas system with a low-profile gas block, and a free-float aluminum M-LOK handguard with a full-length 1913 top rail. The rifle wears a Magpul-branded adjustable carbine stock and includes its owner's manual.
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 minimal markings from prior handling and use. The bore is bright and clean.
What’s Included
- SIG Sauer ROMEO-MSR micro red dot sight (installed)
- One 30-round Magpul PMAG magazine
- SIG Sauer owner's manual
The M400 FORGE series pairs SIG Sauer's AR-15 platform with a mid-length gas system and low-profile gas block for smooth operation. Receiver markings include "SIG SAUER SIGM400" on the upper and "SIG SAUER INC NEWINGTON, NH USA" on the lower, and the factory mfg part number is RM400-556N-16B-FORGE.
The 16 in chrome-moly steel barrel is cold hammer-forged and cut with a 1:7 twist to stabilize a wide range of 5.56mm NATO projectiles. It is threaded and fitted with a prong-type flash suppressor.
A free-float aluminum handguard provides M-LOK slots at 3, 6, and 9 o'clock and a full-length 1913 Picatinny top rail. The rifle includes a forward assist, brass deflector, and ejection-port dust cover, plus an ambidextrous magazine release and a manual safety.
Furniture includes a Magpul-branded adjustable carbine stock and a textured polymer pistol grip with SIG SAUER branding. The rifle accepts STANAG/AR-15 pattern magazines, and one 30-round PMAG is included.
This example comes from the ROMEO-MSR Optic Package, with the SIG Sauer ROMEO-MSR micro red dot installed.