i had a similar situation with my English Springer and a treeing Walker. i first started by having a helper just pet the dog, giving her attention, and treats when she was calm. I introduced a gunnot to shoot but for sight. when she was comfortable with the sight of a gun i used a 5 dollar cap gun from the dollar store and fired shots about 20 yards away from her. the handler did the same as before til she wa comfortable. then i upped it to a .22 LR. after the same process, i upped it to a .410 with light loads. this may take time and dont expose the dog to excessivegunfire. no more than 4-5shots at one session. once the dog was again comfortable, i went to my 12 gauge with field loads that iuse when hunting.boththe dogs were fixed ongun shyness. witha coon hound like my walker, the.22 was all i needed as thats what we generally hunt with for coons. it may or may not work but i have helpedout with 3 other dogs and they were broke of gun shyness. Give ita try, you have nothing to lose