A perforating gun housing includes a housing wall extending between a first housing portion defining a chamber, and a second housing portion defining a bore. The housing wall includes a first outer surface, a second outer surface, and a face extending substantially perpendicularly to the second outer surface between the first outer surface and the second outer surface. A perforating gun tool string comprises a first gun housing coupled to a second gun housing, wherein each gun housing includes a housing wall having a first threaded portion and a second threaded portion for attachment to an adjacent gun housing. A method for assembling a wellbore tool string includes providing a first gun housing and a second gun housing, inserting the second end of the first gun housing into the first end of the second gun housing, and rotating the first gun housing relative to the second gun housing.