Just found the 300 RUM at the local store -used, looks new - with scope for $800. Thinking about buying but just curious what cartridges it can be rebarreled to. Is 7mm rem mag or 257 wby and option or are feed rails on a factory rum too wide?

I have seen used 70 classics in stainless 7mm Rem.for around $450-$550 based on condition at gun shows and gun shops. Seems a bunch of them hit the used racks back when the WSM's and RUM's came out.They also seem to be about as common as green on grass in my area. Have you considered finding one in the caliber you want rather then spending more money to rebarrel one to a common configuration (7MM. Rem.) and then being upside down in the value of your rifle? The 257 Roy is a different consideration all together.
Not trying to be inconsiderate, just my thoughts,
Best Regard's
BD

You're pretty much limited to one of the RUM cartridges, or a 404 Jeffrey. You'd have to change magazines for the others to work. I'd find a 7mm rem mag or 300 win mag if you're wanting an action for the 7mm rem mag or 257 wby, all the right parts are there already. $800 is a pretty stiff price anyways unless it's got a pretty high end scope.

i was thinking of a rebarrel only when original barrel is shot out. i want a 7mm rem mag in the end but could have fun with a rum.

Crow Hunter made some other good points also, though a 7mm Rem rebarrel to a 7mm Mashburn might provide you with some fun also. I purchased a 70 stainless classic 7 RM. Mag. last year for $425 in extremely good condition. I just had to get the trigger worked over a little bit and I like the 26" tube.
I can't say what the fair price for the 300Rum would be, I haven't shopped them, But,if you are looking for an eventual donor mag action I think Crow Hunter was spot on.
Best, BD

anyone know where to find a 7mm rem mag stainless classic for $450?

Well if you really want a Long Range THUMPER you can go the route of a .338/.300-RUM. I believe it is called the .338-Edge and that will take down elk at 800 yards with no sweat.

Rusty I have a 7mm Remington Magnum in a model 70 Stainless with pre-64 action, with a Mag Na Ported barrel but your going to have to cough up a lot more than $450 dollars. This rifle is a real tack driver too!

Why not re-barrel it to 7mm RUM? THAT would be some kind of long range crittersmacker! Either that or a 416 Rigby for a really excellent DGR. No flies on the 300 RUM either, I used one, also a model 70 Classic of course, for plains game on two different African safaris with 180gr TSX bullets as my light rifle and it is a great choice.

I'd do .300 H&H, just because the old classic is neat.

I know of a 300 win mag SS classic that looks like it was left outdoors for its entire life and the owner still wants close to 600 for the rifle alone.