Being shot at has nothing to do with fear of snake bites. Also, not everyone in the military is shot at. It's called an involuntary reflex arc and it's natural to withdraw your hand. Sometimes you can't do anything about it. Point is persistency. I also agree the snake is probably very hungry and his feeding response is fully engaged constantly. If he will take it, offer food every 4-5 days for a month and see if this doesn't calm him down. Hungry snakes are always a bear to deal with.