Cutting coils from 1911 springs has been done enough that you can find folks who have already developed the right answers.
I don't have that info about 3rd gen S&W's, though. Never had a reason to look into it with recoil springs being easily available.
Several years ago I started collecting quantities of recoil springs for the various 3rd gen guns I own and use, instead of just ordering a spring when I thought I was getting ready to need one.
Then a little later I started doing the same with mags and mag springs. I'll periodically order an extra mag, and then a half dozen mag springs, just to keep a running supply building up.