gun for vs track down

gun for

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

  • To strive for the downfall or diminution of another. 

track down

verb
  • To hunt for or locate; to search for; to find. 

  • Used other than figuratively or idiomatically: see track, down. 

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