Hodgdon's data for the .257 Roberts lists a maximum COL of 2.89" for a few loads and less for most and it includes bullets up to 120 gr so they should fit in a short action mag. I was a bit surprised since, as a general rule cartridges based on the 7x57 case are often too long for the Savage short action.
I did a bit of digging and found a letter I received from Savage dated November 6, 1968 (!) replying to a similar question about what other cartridges would fit my .243 Win short action Model 110 (they were all called Model 110 in those days). One of the recommended alternatives was indeed the .257 Roberts with a COL of 2.775" and the 6 mm Rem with a COL of 2.852". So between the Hodgdon data and Savage's own recommendations, your short action should work fine.
Bookmarks