Because the chamber specs and the cartridge specs don't match. If their ammo was the correct size, or their chambers weren't so large they wouldn't have had a problem. .006" is a lot of slop between the cartridge and the chamber. What good does it do to prepare concentric ammo with minimal runout only to throw it in a chamber that starts it into the barrel at an angle?
Had they just necked up a 30-06 to .338 they would have been fine.
