I looks like there are no caisson-pullers here so let me make a guess. They’ll be sure to chime in and correct me.
Velocity is probably the same as you’d expect from any gun or howitzer of that caliber, in the neighborhood of 2600 to 2900 fps. If it uses rocket-assisted projectiles I don’t what the MV would be. 3500?? 4000??? I know very little about the new-fangled weaponry.
The high angle actually indicates a shorter range. Theoretical max range is at 45 degrees elevation but range pattern decreases as elevation increases beyond that. I’d guess they are lobbing that big bullet over a mountain top at a target hidden behind it. That’s what howitzers do.