Pagerank from 301 redirects

I want to 301 redirect my old website which is a PR2 to my new one which is currently PRN/A.
How much pagerank can you accumulate from a 301 redirect? Would I be able to get at least PR0.5? Or maybe even PR1?

It is really very difficult to define How much pagerank can you accumulate from a 301 redirect, because there is no rules of that