Gunshyness is a "man-made" problem -- you'll need to figure out where you went wrong -- my guess is that you should have introduced the dog to gunfire at a much younger age. For good advice on Gunshyness, go to www.coonriverkennels.com then down on the lower left, there is a link called something like "Marks Tips" -- he has an article on preventing/curing gunshyness.

Wayne1 is VERY correct ------- a 5 week old pup doesn't even know it's a dog.
49 days or a bit more is ideal.

And also, Wayne1 is correct------- I'm an expert------ The definition of "Expert" :
Ex = "a has been"
Spurt = "A drip under pressure" [][][]