Can you single-load your rounds in Open F-class? If you can, then you can move the bullet up out of the case for extra powder space, and then there's NO reason to even think about the belted beast. This thing'll flat FLY, given a little extra room. You can easily duplicate the .264's velocities, while Still using a lot less powder. I've got my 6.5-06 throated so that my OAL with a 130-or 140 Berger is 3.440----but ya gotta single-load, for obvious reasons. Recoil is still negligible.
One thing that hasn't been brought up is barrel life. Since the victorian-looking 6.5 retains the parent 30-06's 17'30" (A-square likes to call it 19) shoulder angle, you can expect barrel life to nearly approach human life, as long as you stay with heavier projectiles and medium slow to very slow propellants. Definitely NOT TRUE with the Winny round!
A third thing, that's maybe true for only my home-built, but I suspect may be true for the caliber, is that this thing is so easy to load for. It seems to like everything! I've yet to run a test load through it that approaches 1 minute of angle. My largest group to date has been .898 c/c, and that was with a 123gr Sierra crammed .010 into the rifling, at a maximum of 49 gr of H4350---WAY HOT in this rifle. But my very first test loads with this bullet, .020 off the lands, and 45, 46, and 47 gr of the same powder, went into .258, .454, and .404, respective, while fire-forming cases. My cases are F. A. military match, totally bench rest prepared, but the necks fuzzed to leave them .014 thick per side,(gives .002 clearance in my chamber) and WLR lighters were used throughout.
Yer gonna luv this cartridge!!!! Fegedabadit!!!!
