Soviet heavy SP guns

[Ratzki]

PoorOldSpike

Yes a low vel is fine if you've got all the time in the world to estimate the range,calculate the wind speed and direction, adjust the sights then fire against a stationary target, (remember the assassin in Day of the Jackal carefully zeroing in his sights by popping at a pumpkin?)
But in tank battles there's no time for that.
For example suppose a Pz IV armed with a long 75mm L/43 (740 mps) spots a moving tank at 1000 metres, the gunner simply lays his crosshairs on it and fires, and the shot zips in a fast horizontal line with negligible gravity drop and probably hits.
But if the gun was a short L/24 (385 mps), the gunner could not simply lay his sights on the target and fire, he'd have to first estimate the range and elevate the gun to fire at a point just above and in front of the moving target, hoping that by the time the shell arrived in its slow arcing trajectory the target would still be there.

By contrast, what a luxury for tank gunners to be able to simply lay their crosshairs on the target and fire! Only high-vel guns allow them to do that.

The gunner using a high vel. round would have to do just as many calculations as he would firing a low velocity round, but the deviation from aiming point to contact point would not vary as much. Even a high velocity round moves in an arc from the end of the barrel to the intended target, it is not a straight line. Sights would be zeroed in at what would be the effective range of the gun, then as the round exits the barrel it would be under the aim point by what could be several feet for a specified distance before crossing the aim point for the first time to then being above the aim point by as much as severl feet again, to finally as energy is bled off rapidly crossing the aim point again on the way down to earth. The trajectory is not as pronounced as with a low vel. round, but still exists. Within effective range of each gun there would be little to compare with hit chances. A high velocity gun would be more accurate at it's extreme range the would a low velocity gun at the same range, but at a shorter distance within the low vel. gun's effective range there would be no difference, and the high vel. may be at a disadvantage in some instances dependant on it's on round's arc when fired.