Bataille Empire

When presenting the game to some newcomers, they start to dispute that not allowing ricochet from uphill is not realistic. I tried to find any resource about arty ricochet, but I did not find anything reaonable explaining exactly this topic.

Is this rule based on any particular source?

I cannot remember where I read it. However, I remember something about the ball plunging downward digs in to the ground. I suppose it is like the difference between skimming a pebble across a pond and lobbing it in.

The cannons were firing (almost) horizontaly their cannonballs. The trajectory was a very slow curve, starting at approximately 1 meter high and hitting the ground after 200 to 600 meter (depending of caliber).
The angle was very acute, so the ball had a tendency to ricochet on the ground (exept in snow or mud) and continue its trajectory... for a short course.

If firing downhill, the only case were this could happen is if the slope is continuous, with no horizontal ground (so 8 to 12 UD for the hill model on the table) That's a very specific case, and in almost all the games will not appear.
So if you fire downhill, the balls are assumed to hit the ground and dig in (or reach to the stars,never coming back if firing uphill)

thanks for answers