I had a look at adding extra shot abilities to artillery last week and Its seems that the max abilities you can have is three(including the barrage and accurate fire abilities).I think it a case of remove one to make room for the new.I tried to add round shot to Russian unicorns and was unsuccessful.
Regarding shrapnel shot,I looked in the projectile tables and it seems the shrapnel shot abilitly has been removed altogether.But It wouldn't be too hard to recreate it,but at the exspense of one of the other abilities.
I will investigate further and see what I can come up with.