The 6.5/06 pretty much duplicates the ballistics I noted for the 6.5 Rem Mag., perhaps another 100fps in some bullet weights, like the 140gr.
I think the reason for that is due to the short magazine in most rifles chambered for the 6.5 Rem Mag. & the longer allowed bullet seating in the 6.5/06 with normal 3,340" allowance.
The 6.5 Rem Mag usually has short mags which means long bullets have to be seated more deeply, robbing powder space - with 140's etc.
If loaded to the same working pressure level, the long case 6.5's should be virtually identical to the shorter, fatter 6.5 Rem. Mag.
The working pressure for the 6.5/06 ASquare is 65,000PSI - pezio.
I do not have a listing for the 6.5x65RWS.
The 6.5x57, a German ctg., I think, has a working pressure same as the other 57mm ctgs. at 57,000PSI Pezio.
The 6.5Rem Mag is 63,000PSI, 53,000CUP.

It's strange, whereas the .270 Winchester has a working pressure of 65,000psi, the .30/06 limit is 60,000psi, using exactly the same case. Of course part of that perhaps is the older Springfield rifles in .06, but many higher pressure custom rifles are made up on the Springfield action.