it is do able, when my woodie came to me, she was very gun shy, she would dig herself under my feet to get away. it took alot of work but she's now 110% OK with gun. 
  
I started with woodie by walking her by my local clay ground, not to close to be scared but close enough she could hear them without fear, and slowly got closer, once she was steady with that I started driving to clay ground parking at furthest end of clay ground and sitting in back with her (landrover defnder) and just ignoring the guns, did this for short times 10-20mins depending on reaction and increased it til i had her s