The $575 would be a super deal for a new 4" 629, much less a new blued specialty piece. The bead-blasted blue job is a satin low-lustre. They are pretty - kind of a special piece. Bud's includes delivery at that price, too - not bad.
Don't loosen the strain screw, it is not an adjustment. Doing so will invite, especially in this heavy recoil revolver, continued loosening and ftfs. That screw needs to be all the way down to be tight - S&W will file it and call it 'tuned' in the 625JM & 627 Pro, at least. The lowered spring rate is better. Simply replace the main spring with a Wolff full power - and perhaps a lower power return spring, too. Save the OEM springs. Break-in should improve the smoothness, too.
That's one blued gun that interests me. I don't know why, it weighs a hair more tham my 4" 629, and is certainly not a CCW. Still, congratulations on a neat revolver.
Stainz