It is obsolete when they cease the production of firearms chambered for this cartridge. For example the 300 savage is a very good big game cartridge with a long history of good performance but no rifle has been chambered for this cartridge in many years.
30-06 is still rolling along with healthy sales of rifles and ammo for this cartridge.
Sherwood
Actually Savage was just chambering the .300 Savage in the model 14/114 a few years ago. Now the .303 Savage qualifies as obsolete.
