Hi pat, I'm no expert but here are a few things I have observed after many years of shooting steel targets, mainly with rifles, but some handguns too.
viking is 100% correct, distance to the target is critical for saftey. Unless you are using frangible, (indoor type range ammo).
Gatekeeper brought up a good point also. I've noticed that if the plate is thin enough or soft enough for a jacketed bullet to blow thru, it tends to peel the jacket off and squirt it back toward you. I've seen a steel jacketed 7.62x54r bullet send the jacket back 100 yds with enough force to stick in a mans chest, thru his t-shirt - raised a welt about like a bee sting. The more dense, (harder) steels like AR plate seem to destroy the whole bullet better, avoiding this.
Our group won't shoot steel with a handgun or .22 rifle under 50 yds & 200 yds for high power rifles, but we are real jerks when it comes to safety. We use swinging, weighted plywood frames for pistols in close, like these -
Never tried the knock over silhouette steel targets, too lazy to go reset them.
I've always had access to free steel & a weld shop, downright amazing the crap you can come up with. Good luck with your project, ken
OH, ONE other thing, be VERY careful when shooting .45 ACP ball, I've had that stuff bounce back at me from just about anything, even dirt. When I was in the service we shot tracers out of a grease gun and that darn round would ricochet off trees and everything.