Description
The Sig M400 AR-15 5.56/223 Carbine 16″ Barrel 30 Rd mag is a factory-built, ready-to-run modern sporting rifle from Sig Sauer. It’s a direct-impingement carbine chambered in 5.56 NATO/.223 Remington, featuring a 16-inch barrel, a 30-round magazine, and a mil-spec foundation designed for reliability right out of the box. This rifle bridges the gap between duty-grade performance and accessible civilian ownership.
Key Features
- 16-inch chrome-lined, cold hammer-forged barrel for durability and sustained accuracy.
- Sig Sauer’s M400 enhanced lower receiver with an integrated trigger guard and ambidextrous safety selector.
- Comes with a 30-round Magpul PMAG, a proven industry standard for reliability.
- Free-float M-LOK handguard provides a lightweight, modular platform for lights, lasers, and grips.
- Mil-spec buffer tube and six-position collapsible stock for quick length-of-pull adjustments.
- Includes Sig’s enhanced single-stage trigger for a clean, consistent pull.
Specifications & Details
| Specification | Detail |
|---|---|
| Caliber | 5.56 NATO / .223 Remington |
| Barrel Length | 16 inches |
| Overall Length (Stock Extended) | 35.5 inches |
| Weight (Unloaded) | 6.7 pounds |
| Magazine Capacity | 30 Rounds (1 Magpul PMAG included) |
| Trigger | Sig Enhanced Single-Stage |
| Handguard | Sig Free-Float M-LOK |
The rifle’s 6.7-pound weight, unloaded, makes it easy to handle for extended range sessions or tactical courses. Its 5.56 NATO chambering gives you the flexibility to run both affordable .223 training ammo and full-power 5.56 loads. The heart of the system is the cold hammer-forged barrel—this process creates an incredibly durable bore that resists wear and maintains accuracy over thousands of rounds. That said, the real value is in the complete package. For $798.99, you’re getting a Sig Sauer factory rifle with features that often require aftermarket upgrades on other entry-level AR-15s. The M-LOK handguard is a standout, allowing you to attach accessories directly without bulky rail adapters. It’s a setup that’s drop-in ready for a weapon light and a sling, which are the first two additions most owners make.
Who This Rifle Is For
This carbine is for the shooter who needs a dependable, no-fuss rifle for home defense, duty, or serious training. When it comes to home defense, its maneuverable 16-inch barrel length and proven 5.56 terminal ballistics make it a formidable tool. It’s also an ideal first AR-15—the build quality is there, and it requires no gunsmithing to get started. For the experienced owner, it serves as a rock-solid foundation. Its mil-spec compatibility means every part, from the buffer tube to the fire control group, can be easily swapped with a vast universe of AR-15 components from brands like BCM, Geissele, or Radian Weapons.
Pros & Cons
Pros: Sig Sauer’s reputation for quality is built into this rifle. The chrome-lined barrel and enhanced lower are tangible upgrades over basic models. The included Magpul PMAG and M-LOK handguard add immediate utility. Its overall design is pragmatic, focusing on proven performance rather than flashy gimmicks.
Cons: As a complete factory rifle, it doesn’t offer the customization of a built-from-parts kit. Some may prefer a different handguard length or stock, but these are personal preferences and easily changed later. The single-stage trigger is good, but dedicated match shooters may eventually upgrade.
Frequently Asked Questions
Q: Is the Sig M400 ready to shoot as soon as I get it?
A: Yes. The rifle ships with one 30-round Magpul PMAG. You will need to supply 5.56 NATO or .223 Remington ammunition. Remember, all firearm purchases require an FFL transfer, which we facilitate directly to your local dealer.
Q: Can I use other AR-15 magazines with this rifle?
A: Absolutely. The Sig M400 lower receiver is designed to work with any standard AR-15 pattern magazine, including those from Magpul, Lancer, and USGI aluminum mags. Reliability is excellent across the board.
Q: Is this rifle legal for purchase in Missouri?
A: Yes. This Sig M400 AR-15 configuration is compliant for sale to residents of Missouri and other compliant US states. It is available at firearms-missouri.com for Missouri residents and nationwide, with shipment to your chosen FFL holder.
Look, the Sig M400 delivers a specific kind of confidence. It’s the confidence that comes from a major manufacturer’s QC, a robust barrel, and a platform you can modify as your skills grow. It’s a tool built for a purpose, not a safe queen. If your scenario demands a rifle that works every time you press the trigger, this carbine is a logical starting point. See full details and availability on our product page.
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