Velocity changes seem to change sphere collider radius

hello,

i've been asking allot of questions lately, but i have learnt allot thanks to all the help from these forums, and helpful people..

now to my question..

i have two spheres, one of which is a cue ball. Both balls have the same radius.. if I am shooting the ball very close to the target ball, at a slow velocity it passes by. But the same shot at a higher velocity on same trajectory let's say at 20 m/s hits the target object..

I have no idea why this is happening.

Does anybody have any ideas of what might cause this?

 

To illustrate better i drew these renditions: ..