SAAMI 280AI
My mistake, I was thinking the 6.5x284. Also another optionI believe the 6.5 PRC uses a magnum bolt face.
Another vote for the 280ai or the 6.5x284... those would be my 2 choices
A faster twist 270 win could load the heavy 277 boowits.
I am sure folks with more experience with this particular issue will chime in, but from my brief search, with lead core bullets, you will be able to seat the bullet deep enough to be a non-issue (like the Berger 170 grain EOL Elite Hunter bullet.) But some of those all-copper 'missiles' I've seen can be REALLY long (Hammer 168 grain comes to mind, and it needs a 1 in 7 twist.) Avoiding the longest of those and you can stick with the 'standard' (long action) magazine in that Win Model 70. Or load them long and feed them in 'single shot' style? Not ideal, but the Ruger #1 has killed lots of things over the years and it gets fed one at a time. The 160 grain .270 Nosler Partition would love a little faster twist rate but will seat fine (no need to lengthen magazine length.) Looks like the longest/heaviest all-copper bullet that would work with a 1 in 8 twist would be the Hammer 156 grain, but I don't see a COAL shown for it.<SNIPPED STUFF> I am assuming that heavy bullets for 270 will require some work to the magazine as well to be able to hold and feed them correct?