Does the 7Ultra mag and the 300 Ultra mage share the same case size and shape. I was told you only have to resize the case mouth and it will be the exact same. Is this correct or does the cases have different dimensions such as taper on the case body or a different taper on the case shoulder. If its the same I would think it may need to be trimmed after resize and since its been sized up the neck may be thinner now. Just some thoughts since 300 brass is getting hard to come by.