cast about vs gun for

cast about

verb
  • To plan; plot; contrive. 

  • To try to find; look around; search. 

gun for

verb
  • To pursue as a goal; to work hard to achieve. 

  • To strive for the downfall or diminution of another. 

How often have the words cast about and gun for occurred in a corpus of books? (source: Google Ngram Viewer )