I would choose at least a 200 gr bullet for shooting 500 to 1000 yards. I find the heavier bullets work better and I get a better grouping longer distances rather than lighter ones.
Very interesting perspective. However, since I shot in the World Long Range Championships last year in Ottawa at 700, 800 and 900 metres (with 155 Noslers), and I've been a competitive shooter for a number of years, I have a bit of experience in this area.
I'll reiterate: go with the 168 Sierra, Nosler or Hornady AMAX if you plan to stay inside 600 metres. With a hunting rifle like your .30-06, that's a reasonable maximum. If you use Reloder 22 or IMR 4350, you won't quite get the velocities of your N560 loads, but you'll probably be within 50 to 100 feet per second, and your accuracy should still be excellent. Personally, I'd just stick with N560. Pay a few extra bucks, but keep all your loads consistent. One less variable to worry about.
If you seriously plan to shoot 1,000, you need to use a bullet that was designed for this purpose. There are a number of legendary 1,000 yard .30 cal bullets out there, like the 155 Sierra, AMAX, Nosler and Lapua. The 175 Sierra is also a standout, as is the 178 AMAX and the 185 Lapua Scenar. Of course, the old Sierra 190 has a huge following, but with a bullet like that, you're really boosting the recoil. (I pushed some 190 Sierras once out of my .30-06 with a heavy charge of N560, and I got recoil like a .300 Winchester Magnum -- but it was accurate.)
Do not waste your time with the real heavy bullets: the 208 AMAX, 210 Berger or Sierra, etc.
Of course they work. But you don't need them and they will get you away from the mindset of your hunting loads, which are built around 168-grain bullets. Plus, your rifle is fairly light and you don't need the recoil that these monster bullets will generate. Trust me.
Seriously, David, I'd say just get a Nosler or Sierra 168-grain target bullet and use N560. You might end up with a load that is virtually identical to your TSX load, and even shoots to the same point of impact inside 300 yards. That would be the ideal situation because you could practice without having to change your scope settings at all.
Don't get too carried away with all this 1,000 yard talk.