Sometime in mid October 1965 I was getting a little rest, while leaning against the only bench in the Avionics shop (a tarp strung between two GP tents).   I remember Sgt. Jerry Thomas came running through the shop area yelling at me to get a helmet, because we had a Med-Evac.  I grabbed the first helmet I could find and headed out after Sgt. Thomas.  As we were running toward the flight line, I told tell him that I had never fired the M-60.  His reply was "I'll teach you on the way" and we continued with preflight and take-off preparing for the pilots brief on the way.  Before the pilots could get started with their brief, Jerry ask them if we could test fire the guns.  The HAC replied in the affirmative and we headed out over the water.  Jerry walked over to my side of the aircraft and Very Slowly showed me how to load it and that extra ammo was under the seat.  When the HAC told us it was OK to test the guns, Jerry pointed down and gave me the trigger squeeze sign.  I pointed the gun out the window and pulled the trigger for about a 10 round burst.  Jerry gave me a "Thumbs Up" walked back to his gun pulled the trigger and we started listening to the Pilots zone brief.  When we finished that flight, I remember spending about an hour cleaning up all the expended casings, cleaning the guns and replacing the ammo.