Garand Thumb explores the Masterkey, an under-mounted breaching shotgun typically a modified Remington 870 with an M203 mount, discussing the history, particularly its use by Delta Force, and its applications. He shows how specialized breaching rounds minimize collateral damage and compares standalone shotgun versus Masterkey techniques, demonstrating the effectiveness of various rounds, including civilian and "spicy" options. While highlighting the 12-gauge shotgun's versatility for breaching and self-defense, the he touches on the Masterkey's pros and cons, such as weight and handling, and concludes with potential civilian uses.