Abstract: A hole saw breaching firefighting nozzle may comprise outer and inner housings, a diffuser assembly, hole saw assembly, and drivetrain assembly. The inner housing may be concentrically disposed within the outer housing to create an annular flow region. The diffuser assembly may comprise an end cap coupled to an upstream end of the outer housing. An orifice plate may be coupled to the end cap via linear bearing shafts. A flow control ring may slide forward or rearward between the orifice plate and end cap via linear bearing shafts to control fluid flow communication between the orifice plate and annular flow region. The drivetrain assembly may rotatably couple to the orifice plate. The hole saw assembly may operably couple to the drivetrain assembly. The inner housing may slide forward and rearward. The downstream end of the drivetrain assembly may be in fluid communication with the annular flow region.