Squirrels are blooming hard to hit. Any shots that miss could break a window or windshield.
I do own guns, it is my right as an american. I choose not to shoot willy nilly though.
I still think the best thing is securing the feed and the run from squirrels and trapping mice is the best option.
Perhaps a treadle feeder will help.
https://www.backyardchickens.com/articles/building-a-treadle-chicken-feeder.47900/
I trap and dispose of mice. Not only do they eat the feed they poo everywhere. They carry diseases, fleas and worms to our birds. I have no mercy for them.
Squirrels ...