The CMMG Dissent MK4 in 300 AAC Blackout is a semi-automatic pistol with a 10.5-inch barrel and an overall length of 18.7 inches. At that barrel length, 300 BLK works well with both subsonic and supersonic loads — useful whether you are running a suppressor or not. 
 

Key Specifications 

• Model: Dissent MK4 
• Caliber: 300 AAC Blackout 
• Action: Semi-Auto 
• Barrel Length: 10.5 inches 
• Capacity: 30+1 rounds 
• Safety: Lever safety 
• Grip: Black polymer 
• Sights: Optic ready 
• Overall Length (OAL): 18.7 inches 
   

Detailed Features 

 
The 18.7-inch OAL and 10.5-inch barrel keep this platform tight and easy to maneuver indoors or in vehicle contexts. The 30+1 capacity is standard for 300 BLK, and the optic-ready receiver accepts a wide range of red dots or magnified optics. 
 
The monolithic upper receiver and quick takedown design simplify field maintenance. The lever safety and standard trigger are straightforward to operate, and the black polymer grip holds up well in varied conditions. 
 

Usage Scenarios 

• Home defense and tactical use where the compact OAL matters in tight spaces. 
• Suppressed shooting with subsonic 300 BLK loads, where the short barrel loses little performance. 
• Varmint control and short-range hunting where the caliber's terminal performance is well suited.

The CMMG Dissent MK4 in 300 AAC Blackout gets good marks for its compact size and how it handles the caliber. The monolithic upper and quick takedown feature come up frequently as practical advantages for shooters who clean their own guns or need to pack the rifle down quickly.

The 300 BLK caliber choice is specifically praised by users who run suppressed setups — at 10.5 inches, it stays efficient with subsonic loads, and several owners mention cycling both subsonic and supersonic without issues. Shooting feel is generally reported as smooth with manageable recoil.

Customization gets attention too, with owners noting the platform takes lights, optics, and grips without a lot of fuss. Price is the recurring concern, with some buyers weighing it against other 300 BLK options at lower price points. A small number of users have reported feeding issues with specific ammunition, though this is not consistent across the board. Weight with a full loadout is occasionally noted as higher than expected.