I build many 6.5"s in many cartridge configurations from 6.5X47 lapua through 6.5 WSM and in my opinion the best overall package is the 6.5-284...This is for several reasons-(1)barrel life ,Wsm is 50% (2)consistent day to day ,week to week accuracy.WSM and 264win mag are not forgiving(3) muzzle blast and recoil(4)powder consumption (5)A big game animal down range will react no differently to a bullet traveling 100-200 fps faster(dead is dead is dead)in most situations(6)No custom dies or reloading practices are required for 6.5-284 These are but a few points to consider when choosing.The 6.5X55 and the 6.5-06 are also excellent choices one being slightly faster than the 6.5-284 and one bieng slightly slower.The opinion of the 6.5 - 06 AI being a much better hunting rifle is in the eyes of the beholder,the slight velocity gain in the 6.5-06 AI in my opinion would not be a deal maker.The additional brass Prep initially should be considered as well.In conclusion most .264 dia cartridges are excellent long range performers due to a good selection of high B.C. and high sectional density bullets to choose from.Most of these cartridges have good shoulder angles which minimize case growth.Good luck in your decision making process.If you have any questions i can help with go to
Cloud Peak Gunworks Home Page.