On duty I was suddenly attacked by three Pit Bull Dogs. I was able to draw and "Double Tap" each dog in the chest. The dogs acted like they were not shot, but the noise of the gun shots turned them. Calling for "Back Up" and retrieving my 12gauge we searched for the dogs and found them alive and dispatched them with buckshot. Examining the dogs we discovered that the rounds had traveled though the dogs and exited out the rears. Issue service weapon was Sig-Sauer P-229 .40. Issue ammo was Speer 180 grain JHP ammo. Lesson learn was on a Bad Dog call take your 12 gauge.