The Sig Sauer M400 Sentry in 5.56 NATO (brand part no. RM400-SDI-16B-R5FX) is a semi-auto AR-platform rifle built around a 16-inch barrel and finished in black. Sig Sauer ships this rifle with a Romeo5 G2 red dot sight already mounted, so shooters can be optic-ready out of the box, and fits it with an ambidextrous safety selector. The rifle feeds from a detachable 30-round magazine. Among semi-auto carbines in the AR rifles category, the M400 Sentry favors shooters who want a red-dot-ready 5.56 platform straight from the box.

Key Specifications

• Chambered in .223 Rem/5.56 NATO.
• Barrel has a 1:7-inch rate of twist.
• Built on a semi-auto AR-platform action.
• Features a 16-inch barrel.
• Fitted with an ambidextrous safety selector.
• Ships with a Sig Sauer Romeo5 G2 red dot sight mounted.
• No fixed iron sights included.
• Feeds from a detachable magazine with a 30-round capacity.
• Overall length is 46.1 inches.
• Finished in black.

Frequently Asked Questions

Does this rifle come with an optic? Yes, a Sig Sauer Romeo5 G2 red dot ships mounted on the rifle.

Does it have iron sights? No, it relies on the included red dot rather than fixed iron sights.

Buy the Sig Sauer M400 Sentry 5.56 NATO

A red-dot-ready 5.56 platform straight from the box is exactly what the M400 Sentry delivers. As soon as it’s ready to ship, order it from our Lubbock, Texas gun shop for fast, insured shipping to your FFL.