LineStretcher said:250 yards is the general limit for an ethical kill with the 06. It's not that the rifle can't kill at longer distances, it can but beyond 250 yards you're almost trying to lob the round at the target.
A cartridge isn't ethical to use on game once you start having to correct for trajectory? Am I understanding your statement correctly? If I am correct it sounds like you're talking about maximum point blank range or MPBR.
How about we look at MPBR for the .30-06 and 6.5-300? At maximum point blank range the 6.5-300 Weatherby shooting a 140 grain bullet only has an average of 66 +/- yards more range than a 30-06 shooting a 168 grain bullet on a 10" diameter kill zone. To use your term after 66 more yards you're having to "lob" those 6.5 bullets in as well, because you can't get there without a trajectory correction.
A 168 grain Nosler ABLR with an average muzzle velocity of 2800 FPS will give a MPBR trajectory on a 10" target of 343 yards at sea level. The 6.5-300 Weatherby with a 142 grain Nosler ABLR with an average muzzle velocity of 3300 FPS gets us to 409 yards at sea level on the same size target. Yes I found data that pushes the 140 grain bullets to 3400 FPS and I also had a data that would do over 2900 FPS with the 168 grain, but 2800 and 3400 FPS seemed to be a pretty average across many sources.
I understand your preference and belief in the 6.5-300, but when we look at the numbers neither cartridge is a magical fix for long range hunting. However, I'll put my money on familiarity and confidence in a rifle and shooter using it when it comes to that critical moment of breaking that trigger with a big game animal in your sights. I've spent a lot of time and money looking for my perfect combo of rifle and cartridge, and I've come to realize that I'd have been better off and money ahead if I had just stuck with my .270 Win all along. The .270 while not perfect is certainly capable for 90% of my hunting situations, that's why I suggested the OP stick with his 06.