I had a PH once who said he had a domestic cow to kill. It was behind a small tree faceing him. He said he took a head shot with a solid from a 375 H&H Magnum right through the tree dropping the beast.
For me, if I knew I was going to be shooting through brush, I would be carrying a 458 Lott. If the moose was fairly close to said obstruction and there wasn't too much of it, I suspect a 500 grain Woodleigh would get through just fine.
