Brian,
Been shooting the the 7mm/338 Lapua Short this week (we call it the 7mm LSM or 7mm Fatso, I'll post a pic one day and you'll see why) with 24N41. It proved to be a tad faster than H50BMG, with 84gns of 24N41 behind a 180gn Berger giving 65,000 psi, 86.5gns of H50BMG giving 64,500 psi and 87gns of H870 giving 64,100 psi. These were 3 shot averages after a fouler. Pressure also started to climb quickly as you fired more groups, requiring a reduction in powder charge, similar to 20N29. They must be of a similar composition. You need to be careful of these 2 slowest N powders with max loads judging by my experiences. They produce good velocity though.
Steve,
In perfect conditions you might stretch your 7mm-08 load to 600 yards if the accuracy is good enough, you'd need better than 3/4 moa at 600 yards and preferably 1/2 moa.
The wind is what will get you, if you've done all your other calculations right, and a .48 or thereabouts BC at 2800 to 2900 fps will get blown about a fair bit. From the many deer I've seen killed at long range, I'd be limiting myself to 400 yards with that combo. Of course, I've got bigger guns for the long shots!
You'd have to give me some more specs before I could recommend something, like max. all up rifle weight you can manage, depending on how far you're going to carry it. Also, will you use a muzzle brake? When you combine this with how much recoil you can handle, this will give you an idea of what sort of gun will suit you, and what its capabilities will be. Let me know these things and I'll suggest what I would do in your situation.
Greg