The Mossberg 990 Aftershock is a semi-automatic 12 Gauge shotgun with a 14.75-inch barrel and a 5+1 round capacity. It has a matte blued receiver, black synthetic Aftershock grip, and an M-LOK forend. The 14.75-inch barrel puts this in a short-barreled shotgun configuration; transfer requires additional federal paperwork. 
 

Key Specifications 

• Brand: Mossberg 
• Model: 990 Aftershock 
• Caliber: 12 Gauge 
• Action: Semi Auto 
• Capacity: 5+1 
• Barrel Length: 14.75 inches 
• Color/Finish: Matte Blued / Black 
   

Detailed Features 

• 14.75-inch barrel with matte blued finish (short-barreled shotgun configuration; additional federal transfer paperwork required) 
• M-LOK compatible forend with strap 
• Black synthetic Aftershock grip 
• 3-inch chamber 
• Matte blued receiver

Owners who pick up the 990 Aftershock are typically after a compact, semi-auto 12 Gauge platform, and most report the M-LOK forend and strap setup as practical additions that actually get used. The 14.75-inch barrel makes it genuinely short, and opinions on handling vary by hand size and intended use.

The semi-auto action gets mixed reviews. Some owners cycle a wide variety of loads without issue; others find it particular about lighter loads and recommend sticking to standard or heavier shells. The matte blued finish is seen as functional rather than refined.

Value perception is split. The Aftershock commands a premium over standard pump guns, and not everyone thinks the semi-auto action in this format justifies the cost difference. Those who specifically want the 990 Aftershock configuration tend to be satisfied; buyers who expected performance closer to a full-size semi-auto sometimes feel let down.