I think I would like to look into shooting some swinging steel. I'm thinking maybe like a little 4 or 6 inch "gong" on chains conected to a harness I can just hammer into the ground. Something strong enough for the .308, maximum distance I have to play with is 200 yards at the local range. So, since I know nothing about metal working:

What type of steel?

Is there a minimum safe distance?

Is this something I can make myself or order?