"I think the first real push to do this was the Norco shootout. After that departments started looking for Mini-14's, M16's, and AR-15's. that was about 1980."
This was true on the left coast but not the right coast. I remember that shootout as I was a fairly new LEO at the time. My agency in VA, and many around us, never saw the first patrol rifle until the 2000's. Except for SWAT of course. We were using our handguns and 12 ga's for years. Even now, at least at my former agency, only a few off each squad carries a long rifle. We did go to Slugs (and Buckshot) for the 870's a number of years back which was nice as they are pretty damn accurate up to a certain distance but it's still not a rifle.
"The More People I meet the More I Like My Dog"