Roger that. He's also limited by the lever throw/bolt throw. The -06 (unfortunately) just won't fit. The cartridges based on the 7X57 may not fit either. But there are several good rounds based on the .308, depending on what he wants to do with the rifle. Personally, I like (in reverse order of performance) the 260 Remington, 7mm-08, .308 and the 338 Federal or 358 Winchester. That said, I think the .338 Federal would really up the game of this rifle, both for close woods and for longer ranges out to 350-400 yards. It would require a 24 inch barrel to get the best out of the optimum bullet weights, though. For instance, the Hodgden manual lists a 215 Sierra bullet at 2665 fps or so with Leverlution powder. That would be a hammer, and he would have four more like it for follow-up shots. The impact would be in the 300 winmag range but with a larger, heavier bullet, and the exit wound inside 200 yards would be the size of my fist.
All true. With the right powders, I can get up to 200 fps over most .308 loads. And about the only thing one can do to improve the -06 case design is go to the AI design. It gives a little more case capacity, a lot better case life, and velocity into the lower end of the 300 Win-Short-mag. But its off the subject, because the round is too long for the Savage 99 action.