Dominic, I believe those hay or straw or chaff wads were merely damp, just a little, to allow a mass of that material, unmixed with clay or any other binder, to clump together and act as a wad to hold the shot in place.
Rickk, That sounds like a practical solution, much like a sabot, without the higher cost and complexity of manufacture. I agree with CW, it would be a lot safer as the materials used would essentially be blown to atoms upon firing the piece. It is interesting to note that paper-mache sabots associated with some Civil War projectiles, were the only type of sabot approved to be shot over friendly troops. We infantrymen, had we lived during that era, would not have appreciated getting clobbered by a 5 pound chunk of wood with a flailing iron strap in the back of our heads!!
But what about my assertion that the old artillerymen of that era just had no concern about these slivers of wood, (wedges), because they would be blown into toothpicks by the primo-emergent, (blow-by) gasses? We think that, upon firing, the ball would instantly be ready to fly with nothing of substance blocking it's path. Do you agree or not?
Tracy