When applied to a plasma or Enclave plasma gun, the mod converts the weapon into an automatic weapon, increasing rate of fire and recoil while decreasing range and ammo capacity. It also decreases aimed and hip-fire accuracy.
When applied to a Tesla rifle, the mod converts the weapon into an automatic rifle, increasing the rate of fire while decreasing range and aimed accuracy.
The automatic barrel mod may be crafted and applied at a weapons workbench if the relevant plan is known. It can only be learned from scrapping weapons of the same type.
The automatic barrel mod for the Enclave plasma gun cannot be learned, crafted, or found as a loose mod. It may instead be found pre-applied to Enclave plasma guns, sold by vendors or dropped as a quest reward from the Enclave Event: Dropped Connection.