6 LBS magnums are not very fun to shoot. I realize that it would be a very specialized choice that probably wouldn't get shot except for hunting- but I just don't have that ability- If I have it then I have to shoot it. I handled one of the savage lightweight guns in the store- but haven't shot one- so take this for what its worth. Most of this you can probably tell from a pic- but it is a small gun- the stock feels smaller- and has a series of cutouts in it. The action has been machined down and the bolt is fluted. The barrel is not fluted- but it is a small enough contour that I don't think they could of. The bolt seemed to bind pretty bad on the one in the store- not sure if it was because it was so light or if they removed to much material when they fluted it and it could get a tiny bit sideways. But it fit the bill for lightweight. As you mentioned with the Kimber- they are so light that it almost felt fake.

Another gun that might work is the Howa Alpine. They are around 5.5LBS- I know that they have a 308 win but doubt that they have any long action or magnum options.