Thor's are basically a .500 diameter bullet with a skirt sized to order. They work very well in my .501 & .502 diameter bore rifles. I'm only guessing, but I think it would be somewhat difficult to get the bullet to obturate fully to a .504 diameter bore, even if you could get a snug fit with the skirt. I would be surprised if you could get stellar accuracy with a White. Why not stick with the 460 grain NE or BS conicals the rifle was designed for?