I think it was in "The Hunting Rifle" where Jack O'Connor uses the term obsolete about several rifles/cartridges. In context, I took it to mean they were no longer available in factory rifles, or loaded factory ammo, or were on the way out...not that they were ineffective.
Just think about some of the funky old Winchester lever action cartridges. They would still get the job done, if you could find them.
I think he was trying to keep the target audience from buying a rifle it would hard to keep in factory ammo.
Not a bunch of rifle looneys, who like something because it is rare.
