I've had quite a few standard .257's over the years, which haven't always been standard, so have done some testing with longer throats and various barrel lengths. One was a red-pad Ruger No. 1B with a VERY long throat and, of course, a 26" barrel. It wouldn't shoot any lead-cored bullet under 115 grains very well, but was very accurate with 115 Ballistic Tips at 3100 fps. And no, I wasn't pushing them very hard, in fact stopped there only because that's where my calculations suggested a long-seated .257 could safely go.
