400 yds with a 270 is pretty ambitious. I would definately go with one of the 150gr SPBT's pushed as close to 3000 fps as possible.

To be honest, I would not take a 400 yd shot with my 160gr SPBT 7mm Rem Mag @ 3000 fps.

The biggest problem with an elk is that they require a second shot more times than not. Even with a properly placed broadside heart lung shot. At 400 yds if the bull takes to running, you could find your self in deep trouble - as in the bottom of a deep canyon (and then you will know where the term the valley of the shadow of death came from).

If you do it - bring a fork.

Dsquared