Grandslams have a great reputation of holding up and penetration. I shot a moose with one and penetrated all the way thru. I did with a 300RUM. Another friend of mine uses them exclusively in his win mag.

Only complaint is I usually get poor accuracy with them. But high velocity with no pressure signs. For example my 180gr partition load with 94gr of H1000 in a RUM I had once got less than 3200fps. But same load for 180gr GS, got 3300fps.