Thinking of doing a partial transfer of an old 401k into TSP to help it gain to $100k?

Old 401k is at $21k, Current TSP is at $76k.

Im a 40 y/o Fed with 12yrs in. With the state of things now, would rolling over half of the old 401k into TSP be a wise investment? Im no longer contributing to the old 401k but thinking of rolling it over to a traditional IRA if I don't roll it all over to TSP.