The Mossberg 590 Shockwave is a pump-action firearm classified federally as a "pistol-grip firearm" rather than a shotgun, which means it avoids the NFA short-barreled shotgun designation despite its 18.5-inch barrel and 30.75-inch overall length. That legal distinction makes it an interesting option for buyers in states that restrict SBSs. 
 

Key Specifications 

• Brand: Mossberg 
• Model: 590 Shockwave 
• Gauge: 12 Gauge 
• Capacity: 6+1 
• Action: Pump 
• Barrel Length: 18.5 inches 
• Overall Length (OAL): 30.75 inches 
• Weight: 5.5 lbs 
• Chamber Size: 3 inches 
• Sights: Bead Front Sight 
• Stock Material: Synthetic with Black Finish 
• Receiver Material: Steel 
• Safety Type: Ambidextrous Top Tang 
   

Detailed Features 

The defining feature is the Raptor Birdshead pistol grip, which replaces a traditional stock entirely. This grip changes the handling profile substantially -- the Shockwave is fired from the hip or extended arm rather than shouldered, so technique matters more than with a conventional shotgun. The heavy-walled barrel is designed for extended use without degradation in accuracy. At 5.5 lbs. it is lighter than most full-sized 12-gauge shotguns, and the short overall length of 30.75 inches makes it easy to maneuver in tight spaces. The ambidextrous top-tang safety is accessible for both right- and left-handed users.

The Shockwave generates divided opinions that mostly split along use-case lines. Home defense users appreciate the compact size and the NFA-free classification, while shooters looking for a conventional defensive shotgun find the Birdshead grip awkward without significant practice.

Recoil management is the most discussed practical issue: at 5.5 lbs. firing 12-gauge loads without a stock transfers noticeably more felt recoil to the wrists and hands than a shouldered shotgun. Lighter target loads or reduced-recoil defensive ammunition are frequently recommended for new Shockwave owners. Fans of the platform highlight its versatility -- five choke-compatible loads and a wide range of 12-gauge ammunition give it flexibility despite the short configuration.

The legal classification as a "firearm" rather than a shotgun prompts ongoing forum discussion, with some buyers specifically purchasing it because it falls outside certain state-level SBS regulations. Customization potential (lights, sights, grip accessories) is a popular topic. The price is generally considered fair for the Mossberg platform and construction quality.