Not sure about the sabots but I know for sure the polys did. I used to find them and the powder end had fingers cut into them from the rifling, in fact I reused them by turning them around to see if they would work as well....they did. As far as plastic in the bore, I never had my 12 gage fouled up from the shot wads, maybe your smooth bore is not as smooth as modern shot guns. I have no idea on that I have never owned or shot a smoothie, this is just a guess on my part. Not doubting you at all I just don't know.