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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. Crafting of the mod for all .44 pistols (including The Fact Finder) is unlocked upon completing the Mother of Invention quest.
Learned from script
Stabilized bull barrel (1)
Can only be crafted at a weapons workbench once the required condition is met.
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