Re: .338 lm information
Because the 338 Lapua was a purpose built cartridge from the start with 250 gr bullets, so magazine feeding was never an issue. 300 gr bullets have been used with success utilizing existing magazines for years and attaining great accuracy, so I'm not sure what all the fuss is about.
Berger elevated the 338 jacketed bullet to near maximum potential with it's latest offering but as someone already pointed out, they can still be loaded to magazine length and shoot better than most people pulling the trigger.
There are too many other variables to be concerned with out past a mile for me to worry about the difference of a .4 moa or .6 moa group. If I was loaded at mag length and shot .75 moa groups with the Berger I would be out there putting rounds down range.