I think these are actually labeled as Black Steel on the packages for the bushings.
If they are steel bushings and not cast iron, is there anything to prohibit there use?
The code doesn't say anything about cast bushings or black iron bushings... It says bushings which would include bushings of any type material. For this reason . I choose not to use them.. I don't want to remove & re-pipe when I get turned down...This is the reason I only use bell reducers, reducing t's , ells, etc,