Not all targets are the same. When you’re picking a steel plate, you must figure out what’s going to be shot against it. If you’re shooting rifles, you need a more heavy-duty plate than if you’re shooting pistols. And shotguns are in their own category for setting up plates.
You must be aware of the gate that your plate swings on as well. Setting up a plate on a goat that doesn’t swing easily will lead to frustration as you continue to hit it and it doesn’t register. In that same vein, if you set up too light of a target on a gate with too heavy of a round, the transfer of power might cause the plate to swing over too aggressively and then return.
Take a look at the image below to familiarize yourself with the “if:then” route for a few styles of firearms to determine what steel you’ll need.