Just to put this into perspective... you are discussing stationary paper targets... The Mk13 is about killing the enemy combatants usually at night, maybe on a small boat, sea spray..or dusty, goat shit near by , less than optimal lighting, high angle up or down shooting, dinner sucked and no beers in the previous month... .300 Win Mag with AB43 load in thr Mk13 has a proven record of saving Americans...that is what matters to me to be honest.
Thanks ,, shooting people and paper are different ,most sniper shots are around 100-300 yds. ,the records are a alot of luck when ya calculate wind age ,humidity ,and temp into the cal. heat waves can throw you off by feet and inches .
I am not dissing the 300 Win Mag. But the 6mm is lighter, has better accuracy, less recoil, but less downrange energy though adequate. All the low light is optics, not gun. The 6mm is easier to get hits under any conditions so that is what I would pick. But, I was not on the selection committee so my opinion does not matter. The 300 Win Mag is better for the application than the .308/7.62X51 so that is still a good move. A 243 Win has hardly more recoil than a .223, but has great long range capability so I just think it would have been a good choice and is why it is so often chosen by long range target shooters. If I had to get shot, I would not pick to be shot by a 300 Win Mag.