The Mossberg 590RM Stand-Off is a pump-action shotgun chambered in 12 gauge with an 18.5-inch breacher barrel and a 10+1 round capacity. It has a 2.75-inch chamber, a flat profile trigger, and an optic-ready receiver. The adjustable stock and black finish complete the tactical configuration. 
 

Key Specifications 

• Brand: Mossberg 
• Model: 590RM Stand-Off 
• Caliber: 12 Gauge 
• Action: Pump Action 
• Capacity: 10+1 
• Barrel Length: 18.5 in 
• Color/Finish: Black 
   

Detailed Features 

• 18.5-inch breacher barrel with 2.75-inch chamber 
• 10+1 round capacity 
• Optic-ready receiver 
• Flat profile trigger 
• Adjustable stock

Owners of the 590RM Stand-Off frequently highlight the 10+1 capacity as a key differentiator from standard 590 variants. The breacher barrel and optic-ready receiver are cited as purpose-built features that keep the platform relevant for close-range use, and the flat profile trigger is noted as a comfortable improvement over the standard trigger guard.

The pump mechanism is consistently described as smooth and positive, with owners reporting reliable cycling across a wide range of 12-gauge loads. Some users find 12-gauge recoil at 18.5 inches stout during extended sessions, particularly with heavier buckshot, and note the adjustable stock helps dial in a comfortable length of pull to manage it.

Reliability feedback on the 590RM is broadly positive. The mag-fed configuration is appreciated for faster reloads compared to tube-fed alternatives, though a few owners report needing to break in the magazine feed lips for consistent feeding from the first few rounds.