I rebarreled a .338 WM in a Sako Finnbear with a Douglas 1:12 twist that duplicated the original contour. I'd not go heavier if I were to do it again, but may do it lighter. I've used lots of bullets, but the 225 TSX is nearly a do it all bullet. I've also used 250 grain bullets by Speer, Hornady, Swift and Nosler, and I think there is a bit of an edge for softer bullets for big bears. I've used a lot of 4350 and RL-15 for the 225s, but I think N203-B is a bit better and have shifted to it most recently. For 250 grain bullets I've had very good success with RL-19. I know that some have velocity swings due to ambient temperature with RL-19, but I live in AK and for moose and bears the temp is always 45-55 whether it's spring or fall.
