90% of the new cartridges exist so they can fit in the only rifle worth having to so many people, the AR.....Take that over rated platform away and have your new stuff would be gone.
Old cartridges have stood the test of time because unlike the new cartridges they are made to do a job, not to fit into a specific rifle.
True to a point, but I wouldn't sell the "platform" short. I did for years until I began to notice the accuracy these rifles are capable of. I can remember when they first started showing up at NRA cross the course high power matches. At first they were nothing spectacular in the accuracy department and were even not allowed to shoot beyond the 600 yard stage at some matches due to the fear that the trajectory might drop bullets into the target pits. Then, with a simple change in bbl twist, came the heavier bullets, more accurate at longer ranges and the AR came of age. Not the most beautiful rifle on the line, but no trick at all today to get sub MOA accuracy out of them.
Agree the AR15 is limited to length of cartridges that fit the magazine, but then came the AR 10 for mid-length rounds such as 243 and 308. Now as was pointed out above, someone is making an AR lower to handle 30-06 length cartridges. Did not see where the 300 WM was offered but if the action handles the '06, I'm sure someone will alter a magazine for that as well.
I'll be surprised, short of legislative ban, if the AR's aren't here to stay.........at least until (and if) something else better comes along.
Regards,
hps