From
Clashes: Air Combat Over North Vietnam, 1965-1972 by Marshall L. Michel
"A post-Rolling Thunder official report observed that U.S. guns and missiles essentially had the same low effectiveness in kills-per-firing-attempt - about 13 percent - but the report was somewhat deceptive; in many ways scorned as an air-to-air weapon before the war, the cannon proved very effective. The F-105 scored 20 confirmed gun kills, including two head-on kills, in about 140 gun attacks. Because of the difficulty of setting up the gun sight, about 100 F-105 gun attacks were made without the aid of a computing air-to-air sight, producing about 10 kills, for a success ratio of about 10 percent. The F-105s made about 40 gun attacks with the sight in the air-to-air mode, also producing 10 kills for a success rate of about 25%."
You may be interested to know that gun training has far from disappeared from the syllabus. At an exercise I was involved in just a couple of years ago, I observed (with awe) what happened when 2 F-18s bounced an 8 ship of bomb carts. It was simply calls of "guns guns guns" for about a minute and then right at the end a couple of "fox 2s". The kill-removal stream was a conga line. They claimed, and were awarded, all 8 at the debrief.
I'm not advocating anything here, just telling war stories.
rgds
