i would think any slug would work, but this is what i use ( never tested on an animal, but the sales guy said these work very well and even out of a smooth bore) 5rds - 12 Gauge DDupleks 2 3/4" 1 1/8oz Expanding Shotgun Ammo..
ammotogo.com or cheaperthandirt.com ( i got it from cheaper than dirt.)
realy b2tall.... i have a moss 500a and it fits right in.. i have not shot it yet, but it cycles in and out just fine.