Well, I found a copy of the 2003 Accurate Data for AA8700 which shows compressed loads in 30-06 for 220gr jacketed Sierra Round Nose bullets.
8700 (C) 55.8 1995 62.0 2168
The caveat is to reduce max charge by 2 grains for the 220gr HPBT Sierras.
Seems to me that since the 308's powder column is the same diameter as the 30-06 that a max charge of WC872 under a 220gr bullet would be relatively safe. Honestly I've been thinking about trying to swage down some 160gr 270 caliber bullets to 6.5mm to see if I can't get better ballistics from my swede (maybe even match the old sight ladder).
Machine guns are awesome until you have to carry one.