I'm assuming pretty much the same muzzle velocities from the 140 .270's and 150 .30-06's?
The difference might be in the core hardness Hornady uses in each bullet. A lot of companies vary the lead alloy in the core somewhat for different bullets, depending on the probability of what it might be used on.
I have never used the 140 Hornady in the .270, but Eileen and I have shot a lot of game with the 130 and 150 Spire Points. Most of the bullets we've recovered have been 130's, which makes sense as they're starting out quite a bit faster than the 150's, so tend to open up wider.
The only 150 .270 I ever recovered from a deer was from a whitetail buck shot at about 225 yards through both shoulders. I found the bullet in the far shoulder-blade, the core and jacket just slightly apart. But that was a long time ago, before Hornady bullets had the Interlock ring. If it had been an Interlock it might have gone all the way through, and almost certainly wouldn't have separated core and jacket. I've shot the 150 .270 Interlocks through some pretty big animals, and never recovered one.
