Let me preface this by saying I'm working on loads that are safe for the Garand's gas system, and that can duplicate the M-2 Ball, M-2 AP, and M-1 Ball / M-72 Match loads, so mostly, 150gr - 175gr bullets. For the purposes of this discussion, I'm also limiting my loads to jacketed (gasp) bullets.
So, I've found a powder that has a burning rate that is right in the middle of a bunch of good M-1 Garand powders. (In fact, it is right in between the two "best" Garand powders: Varget and 4895.) But, that company publishes no load data for that powder in 30-06, but they do in 308 Win.
SO, the question is, can I use the 308 load data as a starting point for the 30-06??
Bullet weight is the same, primer is the same, powder charge will be the same. My plan is to work up loads until I get 100% reliable functioning, and velocities are close to the military loads I want to duplicate, and then stop. Of course, I'll be measuring case heads for pressure indicators, but I've found that to be a little less accurate of a pressure measure on the generous-chambered semi-auto service rifles...
BTW, the powder is Ramshot TAC. (Yes, it is a ball powder, and that's why I don't just look at the loads of Varget and 4895 and work from that angle.)