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Sig Sauer M400 SDI is a semi-automatic AR rifle chambered in .223 Remington/5.56 NATO with a 16" cold hammer forged steel barrel and a 30-round magazine. It suits AR shooters who want a ready-to-run rifle with a better trigger, an ambidextrous bolt catch and a durable Flat Dark Earth finish.
Chambered in .223 Remington / 5.56 NATO
16" cold hammer forged steel barrel
Semi-auto action with 30-round capacity
Sig 2-Stage Matchlite Duo trigger
Magpul SL stock with Flat Dark Earth Cerakote
SKU: SGRM400-SDI-16B-FDE · Mfr part #: RM400-SDI-16B-FDE · UPC: 798681714469
The Sig Sauer M400 SDI is a semi-automatic AR rifle chambered in .223 Remington/5.56 NATO, built around a 16″ cold hammer forged steel barrel. It ships with a 30-round magazine capacity and a Flat Dark Earth Cerakote finish.
Several parts set it apart from a basic AR. The Sig 2-Stage Matchlite Duo trigger has a flat blade, and Sig rates the pull at 4.5 – 6.5 lb. The low-profile gas block works with a mid-length gas system. A hybrid compensator/flash hider sits on the muzzle. The bolt catch and release is ambidextrous, so left-handed and right-handed shooters can work it the same way.
Who it suits
This rifle fits shooters who want a solid 16″ carbine for the range, training classes or general AR use. The Magpul SL stock and Cerakote finish give it a practical, ready-to-work setup without a pile of upgrades.
It pairs well with the usual AR gear. Think a red dot or magnified optic, a sling, a weapon light, extra 30-round magazines and a padded case. Because it is chambered in .223 Remington/5.56 NATO, ammunition choices are wide, from range practice loads to defensive loads.
Order online and we ship it to the licensed FFL dealer you choose near you — see how buying a gun online works. Western Sport has been a licensed FFL/SOT dealer since 2007, and everything we sell carries the full manufacturer warranty. Questions before you order? Send us a message.
Frequently Asked Questions
Q: What caliber is the Sig Sauer M400 SDI?
A: The rifle is chambered in .223 Remington/5.56 NATO. It has a 16" cold hammer forged steel barrel.
Q: How many rounds does the M400 SDI hold?
A: 30 rounds. It is a semi-automatic rifle that uses a 30-round magazine.
Q: What is the trigger pull on the Sig M400 SDI?
A: Sig rates the 2-Stage Matchlite Duo trigger at a 4.5 – 6.5 lb pull. It uses a flat blade design.
Q: Is the Sig M400 SDI good for left-handed shooters?
A: Partly. The bolt catch and release is ambidextrous, so it works from either side.
Q: What finish and stock does the M400 SDI have?
A: A Flat Dark Earth Cerakote finish and a Magpul SL stock. The stock is polymer.
Warranty and Manufacturer
Covered by the Sig Sauer factory warranty; warranty terms come from Sig Sauer.
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