Goblin silver is no better at surviving Killing Curses than any other material—the Killing Curse dissipates but explodes the object. However, Harry recognizes that, contra the usual descriptions, this actually means the Killing Curse absolutely can be countered: You just have to put a solid object between you and the curse. Harry should endlessly drill summoning and conjuring solid obstacles to block Killing Curses, including wandless summoning, until his reactions are fluid and effortless; this would stymie a lot of Death Eater combat styles.