can a 300 ultra mag be made out of a 7mm rem mag ? or would this be more work than it's worth?

With Remington chambering the SPS in 300Ultra it's probably more work than it's worth. Factor in cost of the barrel, 'smith costs and the down time on your rifle and it might just pay to buy a Rem SPS.
Cheers...
Con

You need a new barrel, and if the action is a 700,you will need a new magazine insert and the feed rails will need to be modified.I can't comment on other actions.

I bought a new/used Winchester Model 70 in 300 Ultramag for $500.00 two months ago. They are abundant and inexpensive.

lawndart