I have been thinking of getting a smaller, handier rifle for this fall, a sort of mountain rifle in 26 - 30 caliber. The barrels on these can be around 18 - 20 inches, so my question is, what would be a better suited cartridge, an older one such as 6.5 x 55 swede or 7 x 57 that operates at lower pressure, or a more modern one like a 260 of 7mm-08? Or does it even matter?