The 12 Shell Mag is a weapon attachment featured in Call of Duty: Modern Warfare 3 (2022) and Call of Duty: Warzone 2.
It is one of the Magazine attachments available in MW3.
The 12 Shell Mag is a Weapons Platform Specific Attachment, which means it is only usable within its specific Weapons Platform.
Here's how to unlock the 12 Shell Mag attachments in COD Modern Warfare 3 and COD Warzone 2: Get the Bryson 890 to Level 21.
Here you can find the list of Weapon Blueprints that include the 12 Shell Mag attachment in COD Modern Warfare 3 and COD Warzone 2: