Start with whatever air rifle/pistol you have from the time you get the pup. Each time you feed, open the nearest door/window and fire it, then put the food down. Don't make a big deal about it - it is just a normal part of the feeding routine. After a few months progress to your blanks or a rimfire. Same deal, just open the nearest door, casually fire it then put the food bowl down.
Easiest and simplest part of pup training and works a treat every time if you start with a young pup, are consistent and don't make a big deal about it.
