Good advice so far..
I like your choice of calibers the 25-06 also comes to mind as its much better out past 300 yards. BUT that Lil 24 will do you just fine form a dog elimination stand point. Where recovery may not be ultimately necessary.
I would start with something in the 70-85Gr range. The heavier end will really help for those long shots. Longer, streamlined bullets not necessarily heaver bullets will help for those extended ranges. Maybe look at the solid copper jobs out there.
Personally, and its just my opinion, I would steer clear of the ultra lite for caliber offerings out there. Although there trajectories look good. The bullet drift and lower energy figures at impact are not what you need. Don't get me wrong here, they will be Thors hammer out to 300 or so. But past that you may find there performace lacking.
I fooled with this many years ago with my Rem 788 in 22-250. This things was so freaking accurate it was scary. Its primary use was Coyotes, up on the power lines at the back of a piece of private land we hunted. Everytime we set up ON those lines we say nothing. But sit down at the bottom of the hill, some 3-400 yards away and it was grand central station for the song dogs. This was my first experience with bullets completely disintegrating before hitting the target. I had shot them at 100 and they seemed fine but move out to 3 or so and nothing reached the target. I was using SX bullets for the ultimate expansion. I switched to the 60Gr Hornady HPs and toppled them with regularity. Yes I lost velocity, but the longer bullet was plain better at the extended ranges.
I'm not suggesting all lite bullets will vaporize before reaching the target. That's a occurrence that happens because of a barrels rifling and the use of thin jacked bullets going too fast. But the longer bullet is ballistically better for retaining velocity and energy FOR those long shots. Also, much of what I have suggested here would change if you limited your shots to 300 or chose a specific bullet for these extended ranges. (with this caliber)
Good luck and have fun,
CW
