I have a set of used lifters from an LT1. I was messing around with one and took one apart just to see what the heck is in the dang thing. Looks like a spring and a mini piston. Anyway, before I took it apart I noticed that I cannot move the plunger by hand when I push it in with a pushrod. After I took it apart and cleaned it, it was easy as pie to push in the piston against the spring and it bounced back easy as well. So...

Under normal operation, are they supposed to be hard as a rock? Or should you be able to move it atleast a little bit by hand when it's out of the engine?

What about when you get new lifters, should they also be hard to push in, or should they spring back easily until you install them and they get pumped up in the engine?

Just wondering how these things should act...

 

When they fill with oil while running, the oil doesn't compress so it does get hard to compress. That is what opens the valve to full lift. There is a little piddle valve in the lifter that keeps it pumped up but doesn't let it overfill and prevents lifter pump up in normal rpm ranges - a condition that doesn't let the valve all the way back down on the seat.
When lifters are new they are just assembled with a light oil and the hollow body is not filled with oil yet so the little spring inside is all that is supporting the pushrod until the lifter is primed.