You just revived a 12yo thread........friends most recent 257wby project runs 135 bergers at 3475 fps, with a g7 of 335. The heaviest 6mm is 115 w/ g7 of 315. Itd have to be moving over 3775 to match energy at muzzle and distance. Yes the 6mm will be flatter due to velocity, but it still has more wind drift even running 300fps faster. Drops are a few clicks to fix, I'll take the bullet with wind and energy. 257wby case holds around 30% more powder than the 240, you're going up 5% in bullet diameter and only going up 10% in weight. The 240bee is inept in my opinion. My 22" 6mm creedmoor will push 108 elite hunters over 3250, the factory 240wby ammo with a 100gr is only 25fps faster and I'm doing this with 48.5gr of powder.