Gents,
I've never been unable to get a 700 barrel off, especially after I learned to liberally apply acetone to the surfaces to be grabbed on to, ensuring that they are bone-effing'-dry. This helps tremendously with preventing slippage. Follow this with rosin and some cardboard shims, and usually there is not a problem. Some, though, you have to lean on a little.
I could see where the vise in question would work as advertised. I don't think it's going to hurt anything. Bending the ever-loving-snot out of that aluminum might be a concern, though.
Justin