Spiked muzzle brake (Fallout 76)

The spiked muzzle brake is a weapon mod for the double-barrel shotgun

Crafting
Weapon modifications will modify an existing weapon, and any modifications previously equipped on the weapon will be destroyed, not unequipped. Loose mods cannot be crafted. For modifications unlocked through scrapping, the corresponding weapon must be scrapped in order to learn how to craft it.

Location
Crafted at a weapons workbench.