.284, I've been loading .280 Rem for 30 years. Mines a Ruger old tang safety M-77 bolt rifle with a varmint weight barrel.
I just did some experimenting with 30 cal. GMX bullets from Hornady. If you really want to use a mono-metal bullet, I'd suggest you give them a try? They have them in 139 grain weight. They would compare favorably with the barnes tipped TSX, even better, the Hornady is built from gilding metal, not pure copper like the barnes. Gilding metal is what most jacketed bullets use for the jackets, it's 10-15% zinc, which makes it harder, fouls less.
Damn, I just checked Midway, they don't have them in stock, expected on 8-10-09!
Oh well, keep them in mind. Meanwhile here's a look at the 30 cal 165 GMX shot into water filled milk jugs at 3,000 fps @ 100 yds.
As for loads, stick with the slower end of the burn rates, the 4350's up to and including R-22 for the heavier bullets.