Ok first off, I'm not an arty main and I'm not advocating for arty, so put your pitchforks down for a sec. Figured I should probably lead with that lol.
Ok so I'm only two arty missions away from completely acing the first campaign. They both require a lot of stunning, and I've been playing my M44 and not doing all that well (in terms of getting the missions done). So I started wondering if I was playing the best tank for this. So, I looked at the stats, and since I'm a huge nerd, I made a graph of all the relevant information in Python (plus dmg and reload since I wanted to see that too).
So, as you can see, the M12 is by far the best American arty for these missions. I should point out that these figures only assume a 100% crew. No food, equipment, or anything else was used, so these numbers can be improved depending on how you suit up. Also, I only used the top guns.
I hope this is useful. 🙂