Recently someone made a website that shows you how much time you've spent shooting and actually hitting things in CS:GO:
Original post is here.
The script will show an extra column with you hit time over the total time you've spent shooting. It also allows sorting of the table.
Disclaimer: I am not the author of wasted-on-csgo.com, check the reddit thread for the dude. Also, the Steam API is wonky with these stats. This script does not use the Steam API, it just uses the data already on the page.