That's probably because Hornady bullets generally have shorter bearing surfaces than other bullets, thus tend to produce less pressure. You can't use the same data for the 130 Partition that you can for the 130 Hornady Spire Point.
It isn't actually necessay to use H4831SC rather than standard H4831 to get 60 grains in the case. O'Connor used 62 grains of the old stuff, which was bulky, and I used it briefly when I started handloading. Just a little of the mil-surp H4831 was still found on shelves then, and I got 62 grains in the case with no real problem. Though the powder filled the cases right up to the case mouth, seating the bullet compressed it a little with no problem.
Most .270's do indeed still perk with around 60 grains of H4831 (whether long or short) and a 130. Tweaking the load a little to 59 or 60.5 or whatever probably depends on the bullet used and lot of powder as much as the individual rifle.
I have also found R22 and R19 to work about as well--except they tend to lose a lot of velocity at lower temperatures, and H4831 doesn't.
