I would consider a 6.8 SPC. Its case capacity is just slightly larger than the 223 rem but it hits harder than the 30-30. Max powder charges are around 30 grains max.

Trajectory wise its muzzle velocity with the 100-120 grain bullets is similar to the 308 with a 150 grain bullet. At around 2700 fps it has over 1000 lbs KE at 300 yards so it is a real killer despite its small size. See the link for performance.

http://www.doubletapammo.com/php/cat...roducts_id=285

Felt recoil in a 7 lbs rifle is only 9 ft/lbs for this round compared to 18ft/lbs for the 308.