I have seen the gravity feed target by Daisy and the one that uses sporting clay targets. I want to make the same thing, smaller using nicco wafers. Nothing to clean up and they are sufficiently small enough to be a challenge at 50 and 75 yards.
I ran a skill saw set at a depth of 1/8 inch the length of a 2 x 4 and lined up a bunch of poker chips in the kerf. Worked fine but there was cleanup required. I like your wafer idea better than the poker chips.