The ignition problems in the .600 are solved by using a slow burning powder that fills the case so that there is no empty air space.
The ignition problems in the .700 are partly solved by using a filler below the bullet to take up unused empty space in the case, plus putting a grain or two of pistol powder right on top of the primer to get ignition started.
I think the ignition problems in the .700 NE would be completely solved by using a 50 BMG primer, but the cases are not set up for that and I am not sure the firing pin strikes hard enough for them.