well...
644 ft-lbs at 300 yards:
http://www.hornady.com/store/7.62X39-123-gr-ZMAX-Steel-Case/and their .300 whisper load, 622 ft-lb at 300 yards:
http://www.hornady.com/store/300-Whisper-110gr-vmax/But I'll agree it's a lot easier to find good .308 bullets than .310-.312. And the cartridge itself is a better for the AR platform. That's what I'm keeping for a house gun, and I do like the cartridge.
But the 7.62x39 is a bigger case, although held to lower pressures. I wouldn't try it in an AK or even an AR, but a strong action could be warmed up even further.
