I second what Harv said and also nominate the 7mm AM, but there might be a few problems that you would need to decide on.
If you do a search you will see that Kirby has built this round on the Rem 700 action and it works nicely.
Manageable in a 10# rifle......... Don't see why not and especially with a Holland QD brake I wouldn't hesitate to shoot one in a 10# gun all day. Mine weighs a little more than that but I've had a 100# woman shoot mine and she liked it better than her 243.
The criteria that it work in a magazine can be accomplished, it just depends on how you want to seat the bullet and how you have it throated. The picture of Kirby's below shows the round with the 160 grain Accubond and also with the 200 grain Wildcat ULD RBBT's. The gun I had built is throated for the 200's to be seated way out to take advantage of the case capacity. I will also develop a load that is shorter to be used with the magazine, however the primary useage of the gun is as a single shot.
The energy level you want may be a problem [img]/ubbthreads/images/graemlins/frown.gif[/img], as that is about the energy for the AM at 2000 yards, not 1000 yards.[img]/ubbthreads/images/graemlins/grin.gif[/img] [img]/ubbthreads/images/graemlins/smile.gif[/img] [img]/ubbthreads/images/graemlins/grin.gif[/img] If you can live with that then the round might work for you. [img]/ubbthreads/images/graemlins/smirk.gif[/img]
There are a lot of other rounds that would meet your criteria but you asked for opinions so this is just mine. I'm sure you'll get a lot of others and in the end you will still be stuck with making the decision. If your stated energy level is all you require then you can get by with a lot less gun, but you'd be missing our on a lot of long range fun. [img]/ubbthreads/images/graemlins/grin.gif[/img] [img]/ubbthreads/images/graemlins/smile.gif[/img] [img]/ubbthreads/images/graemlins/grin.gif[/img]