That is a massive boolit...
I can't speak for high velocity jacketed rounds, but I've shot over 150 rounds of 44 special and 44 mag into mine so far, and the only thing that has been really chewed up is the backer board for the target. If was to want to shoot a lot of high velocity rounds, I'd probably just use sand. It's going to almost be like hitting a solid rock for the bullet, and they're not going to go in very deep. That 700gr monster of a round would probably need quite a bit of mulch to stop if it's going through two feet of wet sand.