There a are a ton of misconceptions out there regarding Rem 700 actions, more specifically the differences, and lack of differences between actions factory chambered for various cartridges.
While the previous posts have satisfied the OP's questions I'd like to add what I've found from 20 years of tearing down, rebarreling and shooting 700's, probably over 100 rifles torn down and reassembled and rebarreled probably 25 or 30 of them.
I've had RUM's in 7mm, 300 and 338 go thru my hands. They all would feed 7mm Rem Mags and 300 Win Mags without a hitch.
RUM cases will feed out of the mag from a factory chambered 7mm Rem Mag or 300 Win Mag. You will only get two down in the box though because of the lack of cutouts in the walls of the mag.
The followers might be different but it isn't by much and appears to have little effect when swapping cartridge types.
A few other incorrect statements you will hear about 700's.
"The 6.5 x 55 Swede has a bigger bolt face"....untrue, 700's has more than enough clearance in the bolt face to accept the slightly larger base of the 6.5SE....and lots of North American made 6.5 cases have the same rim as a 270 or 30-06.
"You need a magnum length 700 for a magnum cartridge"
ALL long action 700's have the same length mag box whether it left the factory as a 257 Roberts or a 375 H&H....the only significant difference is the bolt face.
"You can't rebarrel a "magnum" action to a standard cartridge"
I put together my first 35 Whelen on a 7 Mag action just by swapping the bolt as I had an extra 30-06 bolt. It fed perfectly.
I couldn't measure any significant difference between the feed rails of a factory 7 Mag and a 30-06 receiver.
The above applies to long actions only.
The long action 700 has to be the most forgiving action made in regards to feeding various cartridges.
