After 16 weeks along, the baby can definitely hear so it will be too loud and sudden for the baby. But even before that you want the mother to have as little as stress as possible as baby feels what the mother does. Shooting may be fun but it includes a level stress and adrenaline for most people, the less experienced the more it will effect them. Probably best to wait until some time after baby is born (and then get a baby sitter of course!).