Go on ebay and see if you can buy two aluminum Oregon splitting wedges and a ten pound sledge.Those rounds won't stand a chance.
I broke one of those spiral round wedges in that stuff. That was heavy metal, aluminum standing a chance in it? I don't know..
The Aluminum cone shaped wedges are what I use to split Elm.So nothing else stands a chance against them.
Update. Splitting with the isocore is hit and miss (no pun intended) lots of thuds on big rounds and oddly some splitting on knotted ones.