Check your local newspaper and browse online ad websites for old swing sets. Many people have swing sets from when their children were younger. They will gladly give the sets away to somebody who is willing to come pick it up, disassemble it and haul it.
Retrieve the swing set and remove the swings from the set. This will probably require a socket set or a wrench. Leave any hooks that are on the crossbar of the swing set. These will give you an easy way to hang your targets.
Go to a local hardware shop and buy about 10 feet of chain. Buy galvanized chain so it does not rust during wet weather.
Go to your local gun shop and buy steel targets. A steel target will stop the bullet and retain its shape under massive fire. These targets should have holes or bolts that let you connect them to the chain.
Connect the chain to the steel targets, then connect the chain to the crossbar of the swing set. Let the target hang from the crossbar. When you shoot the target, gravity will bring the target back to a resting position without you having to reset it.