I built a 340 Wby with a Schneider barrel. If you are stuck on a Remington action, there is not a lot of room for those RUM cases. I modified a Sako Finnbear action and I can load 3.85" rounds into my magazine. I have a reamer that is throated for 300 grain Sierras if you want to borrow it.
I get 3000 fps easy with both Magpro and R17 using 250 grain Berger OTMs. I can't shoot the 300s since my barrel is a 12 twist. If I had to do it again , I would get a 10 twist. I did the 12 as I never intended it to be a long range rifle but wanted the reamer set up so I could with a different barrel and stock. Mine weighs 8# without a scope. I shoot it with no sissy pad and I won't own a muzzle brake. If it had a 2" longer barrel that was heavier you could get it to 10# pretty easy. It would be a pussy cat then!
