Seeing all the post's on gun shyness prompt's me to say a few thing's about introducing the gun. 99 99/100% of dog's are not gun shy. They are made that way. The only reason it's not 100% is that someday a dog may be born knowing what a gun is and that it will make a loud noise that will scare it; that dog has not been born yet!
A dog decide's what it like's by association. If it bring's the dog pleasue it's good, if it induces fear it's bad and avoided. Introducing the gun is as simple as taking your shotgun into the living room and showing it to the dog. Likely the dog will be cautious but soon fully accept this object we call a gun. It's not the gun that scares the dog, it's the noise associated with it!
There is no need to introduce a dog to gun fire until field training is well under way. What's the purpose of risking scaring a young dog with a gun when your still month's away from needing the thing??? If you do and you do it wrong you risk not only making the dog afraid of the gun but anything else it might associate the noise with.
this is not to say you can't introduce a gun long befor you need it. I generally like to start early myself. If your pup is out running around on his own and investigating thing's, maybe it's a good time. But make sure your looking at a pup not intimidated by butterfly's or anything that flies. remember, this a bird dog and bird's fly! there's nothing like a cocky youth and that's where you want pup to be, cocky and reasonably self assured. Do this with lot's of walk's and always take the 22 rifle with you, don't shoot it until the pup is cocky and self assured.
When he's ready, point the rifle at the ground with the muzzle about 4" from the ground. While the pup is away from you and engrossed in something he's shown no fear of, shoot the 22 into the ground. You will get a response but it won't be fear. The pup may be a little startled or meerly look back to see what happened, but no fear. Your about there. Keep doing this for a few week's until pup ignores the sound altogether. The sound become's only a sound and nothing bad has ever happened when it came. Now start pulling the rifle away from the ground and increasing the volume, watch the pup for any sign of fear and back up immediately if you see it. Never praise the pup for not showing fear nor-coddle it if it show's any fear. The noise will then become a normal occurence. If you praise the pup for ignoring the noise and the pup is doing something you'd really rather it didn't do as a grown dog, it'll associate the praise with what it was doing when the shot was fired. That will put you on the road to fixing an unwanted problem later!
Remember that gun fire is just a noise and nothing more unless you make it more. Scream at your pup every time it come's to you and you'll teach it not to come to you. PAY ATTENTION TO WHAT YOUR TRAINING AND NEVER SET YOUR DOG UP TO FAIL!!!!!!!!!!!!