For something really different you could neck down a 7mm LRM. What ever you pick with that powder load you'll need to keep an eye on throat erosion. I'd use as long a magazine as you can to allow room to move to chase the lands. You'll get a little more life out of your barrel.
260 Fat Girl.... you may get a call from the offensive police.We have a reamer on the way that we call the 260 Fat Girl. 6.5-300 Norma mag imp. This will be in the ~85g of powder capacity. A little bigger than what George was wanting. Seems there is a gap in this size. The Dakota is there but brass seems non existent.
We do. Have never Chambered one. Need to, but I have a feeling it could too much of a good thing? 100+ grains of powder. Although @HARPERC 's recent 6.5 Ultracat worked well with about the same powder capacity and not as nice a cartridge. It runs the 124g Hammer Hunter at 3960 fps with Rem brass. He just got an antelope at 90y with it.260 Fat Girl.... you may get a call from the offensive police.
Do you still have the 6.5 Lapua Improved ?