All of the above
I've found that by polishing/lapping the bolts, almost any can be made very, very smooth. The reason you see so many Milsurps listed is because they have been worked many, many times, and have essentially been "smoothed" by all of that use. For example, the smoothest bolt I own is a really, really well used Mauser VZ-24. I also have a Mosin that was really rough...Lapped it with valve grinding compound, then polished, and its smooth as can be, although still not quite as smooth as the VZ-24