similar thing happend to my wheatenxbitch at 11 month, she went throo a stage a being really highly strung and an old van backfired one day we was hunting a quarry, i spoke to a few guys that train gundogs an they told me to gee dog a few weeks off till she was 13 month ish, an start again from start, 1 even geed me a wee cap gun that kids use then i went to air rifle an then a starter pistol, by time she was 15 month she was back to her old self, an would switch on at the sound of a gun, i expect all my dogs to work with a gun