Sawyer buys a hand gun in Australia from a guy named Laurence.  He uses it to kill Frank Duckett who Sawyer thought was the man he was hunting all his life, the real Sawyer.  Laurence tells Sawyer it's a compact 357 with hollow point loads.

Back on the island, Sawyer is the last one to turn over his gun to Jack after the Ethan incident.  Now all the guns, including the Marshal's are back in the Halliburton case.