At 100-150 yards, I would have no problem expecting the 7mm-08 to provide adequate penetration and expansion to kill elk with any hit through the lungs. At this range, the 7mm-08 has about the same energy level as the 7mm Rem mag at 300+ yards and it is universally accepted for this application. Cow elk have much less bulk in the front shoulders and neck and overall lighter weight. A Nosler 140-150 Partition will do the job and get it done quickly. The 7mm-08 has lower perceived recoil thatn the 308 in my experience. I have light carbines in both calibers and have shot and hunted with both. The 308 seems to have a more harsh recoil with the same energy level loading and similar SD bullets.