How accurate is unguided artillery (on its first shot)?

[beowulff]

@Bear_Nenno

Keep in mind, the guns are registered before they are ever fired at an actual target. Kind of like zeroing a rifle, registering the guns allows the crew to make necessary adjustments to improve accuracy of future shots. So once they’re in place, they fire at some known points a few times to get everything dialed in. After that, it’s all computers.

I’m always amazed by this stuff.
Like, how Victorian era battleships were able to hit targets almost over the horizon - from a moving platform.