Please be careful with your steel target. As the target is dimpled, a bullet can strike the edge of the dimple and ride the curved pocket right back to you with significant velocity. This can be hazzardous out to at least 100 meters in my personal and painful experience. Check with a steel fabrication company for some plate that is used in coal mine hoppers or perhaps in gravel pit hoppers. That stuff is harder than woodpecker lips and will cause the bullet to disintegrate on impact. Also, be certain the steel plate can swing freely. This helps absorb some of the energy and saves the plate.
Send me your private email and I will send you a picture of a simple swinging target you cand build or get fabricated cheaply.