I’m a 5th grade teacher (prior military) who is about to start teaching WWI. I wanted to do a compare and contrast of tech then vs tech now. One of the things I am comparing is artillery. So my question is, why did arty rounds go down in size? In WWI, there were 400+mm shells, where as a modern M109 Paladin fires a 155mm. My assumption is that developments in explosive tech meant that the same amount of damage can be done by a smaller round, but I’m not sure if that’s right, or if the fact that modern artillery is much more accurate and there is less need for more BOOM. I also tried to find explosive force equivalents between modern 155mm and WWI era 420mm shells, but was unable to locate. Any input from any current or former 13 series guys would help. I know I’m probably doing way to much research for something that is going to be taught to 10-11 year olds, but WWI and II are the things I actually enjoy teaching