I have a 7mm RUM that I am thinking of reboring. It is a sendero. I was wondering if this would be better than re-barreling.

Mostly opinion and some knowledge, it costs as much to re-bore as to buy a new barrel. You might save a little on the fitting but would still pay the re-chambering. Generally, if the rifle has no collector value and little sentimental value, you might as well re-barrel. Most of the barrel manufactures produce barrels with the same or close to the same as factory contours and, for a extra money, they will duplicate your contour.