A question dear to my heart.

The three best actions I've handled were a Brazilian 08, a Greek Steyr, and a Zella-Mehlis 98.

The Brazilian felt like it was carved from axle grease. Now I have also handled 08s that felt like a usual Turkish k-mart special.

I suspect that it has to do with a very precisely skilled cycle of hardening, alloy, and polish relative to tolerance. Ie there would be the precise carbon (or other lubricating metals) level of the alloy, a precise hardening time and temp (depth of carburation), then a precise quality of polishing (ie dry vs oiled stoning; dry stoning gives higher polish at the same grit). Then polishing at a grit chosen that is enough to be slick but not so slick that it binds. All revolving around specific tolerances.

So for instance measuring the race with pin gauges instead of inside micrometers, using a specific hardening temp and time according to a known alloy. Incidentally it seems like the one constant among best actions is Sveedish steel and milled construction.

My speculations anyway.