Description
Colour is usually the least interesting thing about a rifle. The Sig Sauer M400 SDI Moss Green is an exception, because the finish is the reason most people pick this one over the black or Flat Dark Earth versions of the same gun. It is a muted olive Cerakote that disappears against treelines and brush in a way black never does, on a rifle that would be worth owning in any colour. UPC 798681701216, 1,599.99 dollars at MAG5 Firearms.
The Finish, Honestly Assessed
The Sig Sauer M400 SDI Moss Green wears Cerakote, a ceramic-polymer coating applied thin and baked on. On a Moss Green Cerakote AR-15 it does three useful things: it resists corrosion better than bare anodising on the receiver flats, it takes solvent and oil without lifting, and it breaks up the outline of the rifle in vegetation. It is not camouflage and it will not hide you, but a green rifle sitting against green brush is meaningfully less obvious than a black one.
What it will not do is resist abrasion forever. Cerakote wears at contact points, and on the Sig Sauer M400 SDI Moss Green those are the magazine well mouth, the handguard where it meets a bag or barricade, and the corners of the charging handle. Expect honest wear over a few thousand rounds. Touch-up is possible but colour-matching is imperfect.
The rest of the Sig Sauer M400 SDI Moss Green is the same M400 SDI underneath. Black anodised internals, black controls and a black Magpul SL stock against the green receiver and handguard, which reads as deliberate rather than accidental.
What the SDI Design Actually Changes
SIG built the SDI series around a steel clamp lockup handguard rather than the usual aluminium barrel-nut arrangement. A steel clamping interface resists deflection under load, which matters the moment you lean the forend into a barricade or load a bipod. Point of impact stays where you left it. On the Sig Sauer M400 SDI Moss Green that means the handguard is a mounting platform you can trust, not just a place to put your hand.
The mid-length gas system is the second real engineering choice on the Sig Sauer M400 SDI Moss Green. Compared with a carbine-length system on the same 16-inch barrel, mid-length gas gives the bullet more time to leave the bore before the port opens, lowering pressure at the bolt. You feel it as a softer push instead of a snap, and the bolt and extractor last longer for it. The 1:7 twist handles everything from 55 grain plinking ammunition up to 77 grain match loads.
Third, the trigger. A two-stage flat blade trigger with a defined wall and a clean break, fitted from the factory, is not something you usually get at this price. Add fully ambidextrous safety, magazine release, bolt catch and charging handle, and the Sig Sauer M400 SDI Moss Green is genuinely well specified rather than just well finished.
- UPC: 798681701216, SIG M400-SDI XSeries, Moss Green
- Caliber: 5.56 NATO
- Barrel: 16 in. chrome-moly, 1:7 twist
- Gas: mid-length gas system, direct impingement
- Muzzle: 1/2×28 tapered shoulder, SIG flash hider-compensator
- Overall length: 36.5 in. extended, 33.25 in. collapsed
- Weight: approx. 7.0 lb
- Trigger: SIG Matchlite Duo, two-stage flat blade trigger
- Handguard: free-floating M-LOK with steel clamp lockup handguard
- Controls: fully ambidextrous safety, magazine release, bolt catch, charging handle
- Stock: Magpul SL six-position, reduced-angle grip
- Finish: Moss Green Cerakote receiver and handguard
- Sights: none fitted, flat-top Picatinny rail
- Capacity: 30 rounds, one polymer magazine included
Honest Caveats Before You Buy
Resale is the first thing to think about. Coloured rifles sell more slowly than black ones, and a Sig Sauer M400 SDI Moss Green will have a smaller pool of buyers if you ever move it on. Buy it because you want the colour on your own rifle, not as a hedge.
Accessory matching is the second. Moss green is not a standardised colour, and green furniture from Magpul, BCM or anyone else will almost certainly be a different shade. The safe approach is black accessories, which SIG has already chosen for the stock and controls, rather than chasing a match you will not find.
No optic is included. The Sig Sauer M400 SDI Moss Green ships with a bare flat-top rail and no iron sights at all, so it is not a usable rifle until you add a sight. Budget for that, and for back-up irons if the rifle has a defensive role.
And the usual platform notes: one magazine in the box, direct impingement gas going back into the receiver, and more blowback than you would like if you later add a suppressor without an adjustable gas block. None of that is specific to this rifle, but it is worth saying out loud rather than discovering later.
Who it suits: hunters and field shooters who want a rifle that does not read as black plastic at fifty yards, buyers who already own their optic, and anyone who values the steel clamp lockup handguard and factory two-stage trigger over a bundled package. The Sig Sauer M400 SDI Moss Green is the same capable rifle as the black and FDE versions, in the colour most people actually want. MAG5 Firearms is a family-owned FFL in Collegeville, Pennsylvania, with transfers, cleaning and gunsmithing in-house by appointment.
Browse more rifles in stock at MAG5 Firearms, or read the manufacturer specifications on the SIG SAUER M400-SDI page before you order.
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