I would have to say if your going to the trouble of putting a 30" barrel on the rifle, that you are probably looking for close to maximum velocities with those heavy bullets. In that case i would recomend that you look to the slower ball powders like AA8700, US 869, or some surplus WC 872 (20mm powder, or 860 (50 bmg powder).
Now I was using AA8700 and 872 in my 270-300 Rum (another .007" and it is a 7mm rum), and found that they gave velocities greater than that of powders like H1000 or Re 25 with less pressure. Of course my rifle also had a 30" barrel, but the velocities i was getting were
135 MK 3750fps (working load, 5-6 fireings per case)
140 SST 3715fps (Absolute max 3-4 fireings per case)
150 SST 3650fps (Best load, about 10 fireings before case necks split)
Now you can extrapolate that using a 168gr bullet, the velocity would probably fall in the 3450-3550 fps neiborhood and the 180 close to 3300-3400 fps.
Yah, I know the loading manuals won't show velocities that high, but just remember the barrels they use in their test are usualy only 24-26" long, and that extra 4-6" of barrel can make a world of difference when talking about a fairly small bore like a .277/.284, especialy when your using heavy for caliber bullets.