600w ballast, 400w bulb

Just wondering.
If I buy a 600w HPS ballast, can I use 250w or 400w bulbs in it?

I'm going to be using MH conversion bulbs also.

cheers

no its not a good idea

ahh ok. thanks.
I only grow 1 or 2 plants and thought I could just put smaller bulbs in when they are younger.