The object is to get the dogs focus on the bird not the shot to start with. Put the dog in birds and I mean a lot. Every so often shoot a cap pistol, say 1 in 10 or so. If the dog freaks you have to act like nothing happened. You have to convince the dog it is OK buy doing nothing. Some dogs can handle big ga guns off the bat, I always start with a cap pistol and build from there. Also around the house bang pots and pans around the dog, again nothing is wrong. This may take a while but stay with it.
Gselkhunter