Re: .300 Wby or .300 H&H in Rem 700 ?
I'm a nut for a good H&H. 2900 fps with 200 grain bullets, in a 26" barrel. That said your probably better off with the Weatherby. You can always make 300 Weatherby cases from the H&H, in a long range configuration rifle, with a longer barrel, using heavier bullets I'd say there's enough advantage to justify the extra powder. The 300 Winchester in all reality can't be excluded. With a good barrel/chamber it has way more potential than your current rifle is offering.
I've never been very interested so I can't offer specifics, but I think an even longer magazine is available for the Remington 700. Might be something to look at.
Twist rate is something you'll want to think about, if your going to run some of the longer heavier bullets you'll want to be sure you can stabilize them.
I misread your first post you said nothing of rechambering sorry. I've got a new set of glasses on the way i've been dropping and mixing words.