Re: 600 yard deer rifle
If you truly are not going to reach beyond 600 yards, I'd lean towards the 7mm options. If you want off-the-shelf nothing is wrong with the standard long mag; given the choice, I'd go with the WSM.
Personally I have a bend towards the .30cal options, just prefer the larger bullet I guess. If you're going to include some larger animals or think you may want to go beyond 600yds on game, I'd recommend the 300 magnums.
I have a Sendero in 300WM, it is a fine rifle and developing a load was straightforward. Brass is easy to come by, as is loaded ammo if I ever needed it. I've used it on game out to almost 700 yards and it did not disappoint, it would be a fine choice for you.