I'll have to pick one, but I'm thinking Sierra GK. If I can get the 100 grainers to about 3000, that'll put me on about the same trajectory (give or take an inch or two) as the 65 grain Sierras in the 223 and the 130 grain Noslers in the 270 out to 300 and 400 yards. I like that because I won't have to do much heavy thinking on trajectories if they all shoot about the same.
There is a lot of merit in matching trajectories between rifles. You might be able to match close enough out to a couple of hundred yards past your point blank range. For a discussion, see http://shootersnotes.com/articles/paired-rifles/
Regarding powder, look at AA 4350 -- several folks are reporting 3200 - 3279 ft/sec in 24 inch barrels and 100 grain bullets. That will translate to somewhere between 2940 and 2990 in the 16 - 1/2 inch barrel. Depending on your rifle, you might get a little more, or a little less.