I would add to your list, Quality of Ignition source.
Some semi's, if left to their own devices, become sluggish in the ignition department. It does effect accuracy. This can be a gummed up striker/firing mechanism or just a crudded up breech that prevents consistent bolt closure and headspace. I have a 10/22 with a custom 1-18" twist barrel that will shoot 50M, 10 shot groups on par most of my good bolt guns, as long as i keep the firing mechanism and breech face and bolt scrupulously clean and properly lubricated.
That said, I have a CZ 452 that I can completely ignore, maintenance wise, and it will shoot as well as the Ruger Custom with ammo it favors.~Andrew