The 1957 edition of FM 6-40, Field Artillery Gunnery, has these projected casualty figures for battery and battalion artillery barrages being fired at vile Circle Trigonist opponents. What makes this interesting is that it’s a time period that has all the calibers: The classic old 75mm, the 105 and 6 inch guns well known to later people, the big 8 inchers, and the really big monsters.
Now it’s important to note that these are in absolutely (to the point of being unrealistic) ideal conditions. There’s no cover whatsoever, the fuzes are proximity ones that will explode at the perfect height, and, for what it’s worth, it was made in an era where infantry body armor was far less prominent than it would later become. That being said, it’s still a great resource.