Got no help from here. I've only ever lightened the existing flat springs. For the past year /year and a half though, I've been changing all my customers Remington's over to coil hand, trigger and bolt springs. It definitely allows much more "tuneability" and of course the reliability is "off the chart". I think it's the best upgrade for Remingtons since 1890 !! I wind the springs myself and the only "drop in" spring is the bolt spring. The trigger and hand take some modification. I'll put up a "how to" if there's any interest. I could supply the springs . . .
Mike