I know its an old thread but just thought i'd throw into the pot , I have a 220 swift that pushes the 52g A-max around 4,057 ft/sec av which drops around 5.5 inches at 300 yards when zeroed at 100 yards but i wanted to see how fast i could push the velocity issue without giving anything away to the wind . So i went with a WSM case and a 55g Nosler Bal tip in 6mm which looks as if your sitting a bullet on a dustbin !
I got to 4,300 ft/sec with Norma brass and R15 and 4,400 ft/sec with Winchester brass but the moment i switched to R17 and Winchester brass she hit a sweet spot at 4,530 ft/sec which i stuck with and she drops approx 2.75 inches at 300 yards .
Hope this was of interest to any velocity monsters out there !
Thanks for that.
Been thinking about the 6mm WSM, but with a 1-7.5 twist for DTACs. Might be better off building the 6mm Atlas (.264 Win Mag case), but the WSM case seems more interesting.