While you are at the scrtap yard, do what i did. I got a 14 inch elbow for the city wter system. It is cat iron or ductile iron, I don't know which. It had a two foot piece of Pipe attached to it. I welded the iece of pipe to a flat piece of 1/4 inch plate, and I welded casters to the bottom of the plate. I now have a bullet trap that weighs six hundred odd pounds. It rolls around, and will catch any handgun bullet i have tried in it, up to a 44 magnum. I just use the lead over, and over, and over.
I teach concealed carry classes. I have a .22 caliber bullet trap bolted to the back of my target stand where the students Qualify outsdide on nice days, and in the basement on rainy days. I have a sandbag wall behind the target astand, and walls, and a 6x6 ceiling over the shooting lane. I have only had three bullets that missed the trap, and those just barely. They went harmlessly into the sandbag back stop. The best part is that I catch all those nice 22 LR bullets for my .38 target loads! Same thing with them; I shoot them into the .22 bullet trap and I have more and more lead all the time, instead of less and less. The only real drawback is that i can't shoot the magnum outside, but shooting in the basement keeps the noise down. .38 target loads aren't as loud as high velocity 22s, in my opinion. I am sure that this is not reccomended, But I have never had a whole bullet come back out of the 22 trap. Again, I only use midrange wadcutters, at about 800-850 fps. I imagine a 357 would badly dent, or even perforate one of the commercial bullet traps. The magnums I shoot into the water pipe elbow. It keeps soft lead with soft, and hard with hard.
You should ALWAYS Use safety glasses when using a bullet trap of any kind, because of the lead particles that WILL fly back. hanging a piece of rubber pond liner over the trap helps with that, too.