An extensible adhesive dispensing gun system. A syringe has a piston for urging an adhesive out of a nozzle, and a first mount at a back end of the syringe. A gun body contains a mechanism for advancing a plunger from a front end of the body in response to a trigger, and a second mount is disposed on the front end. An extension tube assembly includes an outer tube having near and far end adapters. A third mount on the near end adapter engages the second mount on the gun body, and a fourth mount on the far end adapter engages the first mount on the syringe. An inner rod member is arranged inside the outer tube. When the gun plunger is urged against a back end of the rod member, a leading end of the member forces the syringe piston to urge the adhesive out of the nozzle.