Honestly I don't care what anybody uses, I just don't like non-substantiated BS.
I load for a friend's 6.5C and I load for my .260Rem (+ 30 other calibers). With 140s and a 24" barrel the 6.5C is a 2750 or so MV (which is actually being generous).
Spaulding's actually correct, he ran his numbers with both cartridges using their highest BC bullets.
As for MVs:
Nosler Lists 2730 as max in 6.5C with a 142 :
https://www.nosler.com/65-creedmoor
Nosler also lists 3020 for a .270 with a 140:
https://www.nosler.com/270-winchester
Using Strelok Pro and the same environmental conditions with a 10mph 90 degree wind:
For the 6.5C I used a AB Long Range with BC of .625
500 yds 6.5C 39.5" of drop and 20" of windage at 500 1346 lbs of energy
700 yds the 6.5C has 105.5" Drop, 28.0" of windage and 1056 energy
The .270 Win I just used a plain old 140 gran AB with a BC of 0.496
500 yds 34.2" Drop 15.6 Windage 1412 energy
700 yds 93.6" Drop 32.4" drift 1042 energy
IF I was worried about LR with the .270, why not go with the 150AB LR bullet and a BC of .591 and a MV of 2900?
500 drop 35.0 drift 13.4" 1571 energy
700 drop 93.8 drift 27.4" 1221 Energy
Of course there could be some variations, fast barrels etc., but a freaking 6.5C is not catching a .270W anywhere close to 200 yds no matter how many time jmr40 posts it.