I was fooling around today loading buckshot for the 12 and had some .512 lfngcs for my linebaugh that run about 500 grain sitting on the bench. I put one in a 20 guage wad and put that wad in a 12 guage wad. It fit kind of sloppy and i doubt youd get any accuracy. 500 grains works out pretty close to 1 1/8 so i shot it with a mild load of 14 grains of redot and it went bang. I started fooling around and found some wads for 1 1/2 once twenty guage loads. the bullet fit great in it and it was a good snug fit in the hull. Its to deap in the hull though and i dont have any 20 guage felts to bring it up so i kind of shelved it till i get some felt wads. Sure would make a hell of a short range stopper for the 20 guage though.