capper - yes, the do work great! I haven't used spent shotgun shells in years - mainly because I don't even own a modern (cartridge) shotgun with the exception of a single 410 that I keep around for critters. When I was a kid, we had a Winchester 410 pump so we always had a good supply of empty shells. Of course those we shot at with the 22 but at a much closer range. I probably couldn't even see 'em now without a scope!
Suckers make a great target as well - either the flat kind or even the Tootsie Roll Pops. A scrap 2 X 4 drilled for the paper "sticks" allows 'em to stand up. I had a scoped CVA .32 caliber "squirrel rifle" one time that was a hoot to shoot at 25 yards - it was an accurate little gun and it would explode the suckers without a problem. I sold it and now wished I had kept it. I like using the "game" targets but placing them out at various odd distances - i.e 20 yards, 32 yards, etc. - makes it interesting with my 36 H & A under hammer as a person kind of gets used to how their rifle shoots at say 25 or 50 yards but let's face it, varmints don't always appear at "set" distances!