didn't think lead would shoot through stainless steel so easily

I saw this home made steel plinker spinner on utoob so I decided to make one. Shooting stainless steel spoons with lead pellets I thought this would last indefinately. Boy was I wrong. I set up only about 40 yds away and every shot went clean through every spoon. They must have been using .177 because I used some jsb .25 heavies 33.95 gr. And like I said, clean through. Now Ihave to rethink my design.