Stihl 090av vs BIG OAK - Removing Rootball

Had to separate the rootball on a BIG old Oak. Tested out my second Stihl 090AV that I had just finished rebuilding. The bar/chain is 4ft long,.404 .063 full chisel, thats the longest bar I had at the time. The MS660 Magnum I used at the end, was newly rebuilt and I hadnt tried it on wood yet. Didnt get a chance to really test it on this tree. I did not cut the trunk lower to the ground, because I found 3 strands of Barbed wire embedded in the base. Next step. Slab the trunk.