Here's an interesting OLD stat from an OLD US Dept. of Justice publication:
"(Automatic) pistol production grew from 28% of the handguns produced
in the United States in 1973 to 80% in 1993."
Now, that's only guns PRODUCED in the US but, still, we can see that there was a big shift towards autos during that time period.
Here's a link to that report:
www.bjs.gov/content/pub/pdf/GUIC.PDF