Re: 4 target gong set
Thanks for putting this image up - the target holder system is simple, strong and takes less than five minutes to assemble. We also use old swing sets but this is simpler.
Used to use 2"x4" wooden saw-horse setups but the fragments chew up the wood and imbed so you had to wear gloves or get cuts.
I like to use the big hanging target for zeroing and smaller free-standing ones for knocking over (killing) - have a bunch of both. So far do not have any hard steel, you can see the bumps and divots but they are cheap and easily replaceable. We recently got some 3/4 and 1" targets, shoot them at 400 and make some nasty divots but no penetrations.
Do not feel comfortable shooting at steel closer than 400 yards, plus the way we hang the steel the shrapnel goes downward, never have anything coming back.