Lots of interesting comments here. As Mule Deer has pointed out (not for the first time), there really hasn't been any truly new cartridge for quite some time.
I have been caught up by a couple of the "new" chamberings introduced in the last 20 years, most notably the 204 Ruger, the 375 Ruger, and a couple of 6mm's.
I've sold all of the 204's off except one rifle, which is an AR with a long, heavy barrel that I bought especially for varmint hunting, and it's the only 204 I've kept. I don't hunt varmints much any more, so it may not survive the next gunsafe purge either.
I got rid of all the newfangled 6mm variations I got caught up with, and have instead been enjoying exploring an old 6mm caliber, the 243 Winchester. I've bought a couple of nice 243's that work so well for myself and for the young ladies in my family that I expect I'll continue exploring this caliber for another decade or more.
I had a 375 Ruger rifle that I ended up replacing with another hoary old obsolete caliber, the 375 H&H... in fact, I got rid of the new Ruger so I could take an "old" Holland & Holland to Africa this past summer and killed Cape buffalo and kudu with that obsolescent cartridge in a Mauser-action Kimber, said action being yet another ancient intrusion into my riflery.
And now I'm looking at all the 308's occupying space in my gunsafe that I don't shoot any more, because I've started playing with 30-06's instead.
I seem to be going backward in time...
