Metal balls pile, not rubber balls

I am stumped.
I have multiple objects that fall on each other. as they collide due to gravity , the more on top the more the bottom objects are distorting like they are being crushed. I call this the rubber ball effect. I do not want the mass of the objects to effect each other .
I need them to pile like metal objects not rubber objects.

I have applied a metal material to the sphere colliders and that does not do it.

Well i found the solution, Just not sure why.
I had objects that would stack up, and depending on their tags would react through the ontrigger event.
the ontrigger script was triggered on the sphear colider.
as the items stacked they seemed to gain more and more mass and would crush the items on the bottom of the pile. This was not intended.
Solution: I unclicked use as trigger on the sphere colider and clicked use as trigger on the mesh colider. All works fine now.
Wierd ha?