Oh boy, there are some images I didn't need in my head. To get back on track, wonsky touched on something I had to learn the hard way: beware of light rifles and big cartridges. I love a light rifle, BUT there are some cartridges that are just too much for a lightweight rifle. Especially I speak of light barrels. Too light of a barrel equals a lot of muzzle jump which does no favors for accuracy in the field. Also, light barrels can cool quickly at the muzzle while the thicker area near the chamber stays warm which results in bad stringing when you are sighting in or doing load development. When you shoot them you have to go slow: fire a few, let it cool all the way, fire a few more. I personally won't own another rifle with a lightweight barrel. I'd rather have a medium weight sporter with a lighter stock, but that's just me.
Just to clarify, if I were looking for a magnum type rifle I wouldn't be shy about having extra weight all around in the neighborhood of 7 pounds plus without scope (maybe a wood stock is better in this case?) and I certainly would not give up a medium weight barrel to save weight.
If I wanted a light weight rifle in a chambering that made sense for a lightweight rifle (say a 308) I still would not give up a medium weight barrel regardless and would rather get a lighter stock. There might be a balance issue, but probably not. I have been shopping rifles to death the last few months and the medium weight, longer barrels feel just as balanced as anything. Just and opinion though - others will vary.
I haven't checked into any .257 Weatherby mags. I'll have to do that this weekend when I get some more time.
as for the barrel, its no big deal to me if it puts on a few more pounds that will make the gun perform better. Bigger is better for sure with barrels.