I found this fascinating, it's the national archives database of Gunfire Support During the Vietnam War and here is the Edwards. (I started with the page that was during my dad's time)

It has every report of every incident of gunfire; duration, rounds, target, target distance, type of target, etc.

https://aad.archives.gov/aad/display-partial-records.jsp?dt=842&sc=18067,18087,18090,18091,18092,18093,18096,18100,18101&cat=WR28&tf=F&bc=,sl,fd&q=&as_alq=&as_anq=&as_epq=&as_woq=&nfo_18067=D,6,1966&op_18067=3&txt_18067=&txt_18067=&nfo_18087=V,6,1900&op_18087=0&txt_18087=&nfo_18090=V,16,1900&op_18090=0&txt_18090=edwards&nfo_18091=V,4,1900&cl_18091=&nfo_18092=V,4,1900&op_18092=0&txt_18092=&nfo_18093=V,1,1900&cl_18093=&nfo_18096=V,13,1900&op_18096=0&txt_18096=&nfo_18100=V,2,1900&cl_18100=&nfo_18101=V,2,1900&cl_18101=&mtch=1353&rpp=50&pg=20

I checked out this url and found that we on the DD950 were firing at a "cave" in March 1965. Round the clock, every five minutes, ka-BANG! The five-inch fifty-fours recoiled like a ten-ton sledge hammer hitting the ship but we learned to sleep through it. No choice. We'd refuel at night and stand a four-hour sonar watch at night so we were fatigued at sea.
Here's a good Vietnam War naval novel with a true to life gunfire support episode and then a Tonkin Gulf attack.
http://www.amazon.com/Allen-Meece/e/B004HCF95S