The Collaborative International Dictionary of English v.0.48:

gun for \gun for\, v. t.
   1. To pursue with the intent to kill.
      [PJC]

   2. Fig. To make an effort to harm someone, especially with
      determination; -- also used humorously.
      [PJC]

Moby Thesaurus II by Grady Ward, 1.0:

54 Moby Thesaurus words for "gun for":
   angle for, ask for, beat about for, charge, cock, delve for,
   detonate, dig for, discharge, drop, eject, fell, fire, fire off,
   fish for, follow, go gunning for, gun, hit, hunt, hunt for,
   hunt up, let fly, let off, load, look, look for, look up, pelt,
   pepper, pick off, pistol, plug, pot, potshoot, potshot, prime,
   prowl after, pursue, quest, riddle, search for, see to, seek,
   seek for, shoot, shoot at, shoot down, snipe, still-hunt, strike,
   take a potshot, torpedo, try to find