You should have no problem getting 3000 FPS with 120's out of the 6.5x55 w/ Re17 in a strong action rifle. Alliant lists 44.0gr of Re17 as the max load for the 260 Remington. In a T3, I'd use that as the starting load and carefully work up. I've used Re17 with moly coated 108gr Lapua's and was getting 3150fps out of my Sako 75 (same barrel as the T3) with no pressure signs.
If you can't get the velocity you want w/ Re17 try N550 or N560. With N560 I push a moly coated 130gr Swift Scirocco II at 2950fps quite nicely out of my Sako. As far as I can tell (and God knows I've tried a lot of loads) it's one of the flattest shooting 6.5x55 hunting loads out there.
If you're going to use the load on game I highly recommend the Swift bullet. The Swifts are a little more pricey then the Nosler's but they sure do perform a hell of a lot better on game.
