What religion? I know several priests and ministers who enjoy hunting and fishing. Is he Christian or Jewish? Both religions are full of examples of religious figures killing animals for food. I suppose some forms of Hinduism and Buddhism forbid the killing of anything, but only the most extreme believers follow it.
Often, religion is used as an excuse to cover a fear or insecurity about weapons. Show your father a high level of responsibility, enroll in a hunter-safety course, and have an informed and level-headed talk with him. After a few initial talks, try inviting you g-friend's father over so he can further convince your dad that you will be safe and looked after.
Be patient and don't get angry, but remember that some people refuse to change their minds. If so, you'll just have to wait until you are on your own. Talk to you girlfriend about going to college in a firearms-friendly state (or just move and get a job). In most states, an 18 year old can walk into a store and buy a rifle reguardless of what their parents say.