RE: Puppy is busting birds...
Some may say that six months is too early for training but I don't. Alot of trainers are will take a six month old puppy as long as they have all their adult teeth. Just don't expect the puppy to listen well as it will be distracted alot. But you seem well ahead of the game since your pup already has the bird drive and knows gunfire.
I would start planting birds and start using a checkchord and start reinforcing the commands in the field. Any pointing dog book would prolly help.
As to your dog having a hard mouth, there's alot of different ways you can try to prevent this but most methods don't really work (from putting nails into a dal rod and FF to using cigarettes). Someone more familiar could probably help you here as I never cared if the dog brought it back to me dead or alive; I'm just happy my dog brings it back to me.