An ethical shot is based strictly on your rifle/bullet combination and your shooting ability. Is it ethical for me to shoot a running deer? Depends doesnt it? Can you make the shot? Is your bullet capable of delivering a clean kill? Lets face it, some folks just arent very good shots. They may not be able to practice enough. They may have never learned how to really shoot. What is ethical for me to do may not be ethical for you to do. Simply because you draw you limit at a 100 yard shot doesnt mean I can not kill cleanly at 200 or 300 yards. If I can kill cleanly, isnt that an ethical shot? Of course it is. I never take a shot that I am not 100% sure I can make. I am certain you do the same. The difference may well lie is what we, as individuals, can do with a rifle.
My point is, that if we were out hunting and I handed you a rifle to shoot a deer, would not knowing what caliber/bullet you had(assuming a deer rifle, deer at 100 yards distance not an issue ) change where your aim point was. I honestly dont think it would make a difference making an ethical shot.
If you handed me a strange rifle, I wouldnt take any shot. That wouldnt be ethical.