SIG SAUER MCX Regulator Semi-Auto Rifle RMCXR556N16B — Description

The SIG SAUER MCX Regulator RMCXR556N16B is a modern 5.56 NATO semi-automatic rifle that combines the proven MCX platform with a traditional ranch-rifle configuration. Designed for versatility, reliability, and practical field use, the MCX Regulator features SIG Sauer’s short-stroke gas piston operating system, a redesigned lower receiver, and a classic Magpul SGA 590 stock configuration.

Unlike traditional AR-style rifles, the MCX Regulator uses a compact MCX operating system that eliminates the need for a standard buffer tube, allowing the rifle to use a fixed traditional-style stock. The Magpul SGA Mossberg 500/590-compatible stock provides adjustable ergonomics, while the rifle’s aluminum receiver, free-floating M-LOK handguard, and integrated ARCA rail provide a lightweight and adaptable platform for hunting, ranch use, and precision shooting.

The 5.56 NATO configuration features a 16-inch cold hammer-forged barrel, Coyote/Gen II NiR FDE Cerakote-style finish, fully ambidextrous controls, SIG’s two-stage match trigger, and compatibility with standard AR-pattern magazines. The rifle ships with a 10-round magazine in this configuration.

SIG SAUER MCX Regulator RMCXR556N16B — Specifications

Manufacturer: SIG SAUER
Model: MCX Regulator
Model Number: RMCXR556N16B
Caliber: 5.56 NATO (.223 Remington compatible)
Action: Semi-automatic
Operating System: Short-stroke gas piston
Platform: MCX modular rifle system
Barrel Length: 16 inches
Barrel Material: Cold hammer-forged carbon steel
Barrel Twist Rate: 1:7″
Receiver Material: Aluminum
Finish: Coyote / Gen II NiR FDE Cerakote-style finish
Stock: Magpul SGA 590 stock
Handguard: Free-floating M-LOK handguard
Trigger: SIG SAUER two-stage match trigger
Magazine Type: AR-pattern detachable magazine
Magazine Capacity: 10 rounds
Controls: Fully ambidextrous magazine release, safety selector, and bolt catch
Muzzle Device: SIG-designed compensating muzzle brake
Rail System: Full-length Picatinny rail with integrated ARCA rail
Overall Length: Approx. 39.1 inches
Weight: Approx. 7.9 lbs with magazine

Key Features

• 5.56 NATO chambering with AR magazine compatibility
• MCX short-stroke piston system for reliable operation and reduced fouling
• 16-inch cold hammer-forged barrel for durability and accuracy
• Traditional Magpul SGA 590 stock for improved field ergonomics
• Coyote finish with reduced infrared signature coating
• Fully ambidextrous controls
• SIG two-stage match trigger
• Free-floating M-LOK handguard for accessories
• Integrated ARCA rail for tripod and precision support use
• Optics-ready Picatinny rail
• 10-round magazine included
• Modular MCX-compatible lower receiver design

Package typically includes:

• SIG SAUER MCX Regulator 5.56 NATO rifle
• Magpul SGA 590 stock
• 10-round magazine
• SIG muzzle brake
• Owner’s manual and safety documentation