It's the coolest sounding out of all the 6.5s that's for sure.
I have a pre-64 Model 70 in 264 magnum. Stainless barrel so it'll take the hotter loads if I wish to reload some hot ones. To me, the 264 compared to the 270 is similar to comparing the 30-06 to the 300 Win mag or H&H mag.
I got my first crono when I was shooting my second 264 a lot and shortly after that I started calling the 264 a 270 Winchester with a belt and boy does that get 264 fans riled up! Frankly, if your getting a 140/264 bullet over 3000 to 3050 fps from a 24 inch barrel then your doing well from what I've seen.
I've owned 7mm rem mags and I agree with those who say it's a better choice than the 264 but I'll reiterate what I said before about the Weatherby cartridges, the 257 and 270 Wby's are closer to the 264 caliber than the diameter of 7mm and outperform the 264 by a wide margin if velocity is what your after.
Have an older rem 700 in 264, stainless 24" barrel, 73 grains of H870 with 140 bullet would not make 2900 fps. Been sitting in the closet since 92. Went out and bought a 270, less powder same speed.
H870..... it's been a while since you reloaded that!
Some say that the newer powders get better performance out of the 264 but the load data I've looked at doesn't reflect that claim.
That is because the manuals that list new powder have been dumbed down.